阅读说明：本技术 集成相干光学收发器、光引擎 (Integrated coherent optical transceiver, optical engine ) 是由 拉达克里希南·L·纳加拉扬 于 2020-03-17 设计创作，主要内容包括：本公开涉及一种集成相干光学收发器、光引擎。相干收发器包括单硅光子基板,该基板被配置为集成倒装的并与波长调谐部耦接的激光二极管芯片以提供具有调谐波长的激光输出,该波长以X：Y比例被部分分成本地振荡器信号进入相干接收器块和光源进入相干发射器块。相干接收器包括将相干输入信号分成分别由两个90度混合接收器检测到的TE模式信号和TM*模式信号的偏振光束分离器旋转器,和由两个来自可调谐激光器装置的本地振荡器信号辅助的倒装TIA芯片。相干发射器包括倒装在硅光子基板上的驱动器芯片以驱动一对Mach-Zehnder调制器和正交相位分支中的90度相移通过I/Q调制将激光输出调制为两个偏振信号,并使用偏振光束旋转器组合器将它们组合为相干输出信号。(The present disclosure relates to an integrated coherent optical transceiver, optical engine. A coherent transceiver includes a single silicon photonic substrate configured to integrate a laser diode chip flipped and coupled with a wavelength tuning section to provide a laser output having a tuned wavelength, the wavelength being measured at X: the Y-ratio is partially split into a local oscillator signal into a coherent receiver block and an optical source into a coherent transmitter block. The coherent receiver includes a polarization beam splitter rotator that splits the coherent input signal into a TE mode signal and a TM mode signal, which are detected by two 90 degree hybrid receivers, respectively, and a flip-chip TIA chip assisted by two local oscillator signals from a tunable laser device. The coherent transmitter includes a driver chip flip-chip on a silicon photonic substrate to drive a pair of Mach-Zehnder modulators and a 90 degree phase shift in the quadrature phase branch to modulate the laser output into two polarized signals by I/Q modulation and combine them into a coherent output signal using a polarization beam rotator combiner.)

1. An integrated coherent transceiver comprising:

a substrate member;

a tunable laser device including a laser diode chip having a gain region, a p-side electrode of the laser diode chip being inversely mounted on the substrate member, the gain region being coupled with a wavelength tuning portion formed in the substrate member to tune a wavelength of laser light output from the gain region to a waveguide in the substrate member;

a first power splitter coupled to the waveguide to split the laser light into first and second light;

a coherent receiver block comprising at least two 90 ° hybrid receivers respectively coupled to two outputs of a polarization beam splitter rotator in the substrate member to receive a coherent input signal from a coherent optical network and to two outputs of a second power splitter to receive two local oscillator signals split from the first light to assist in detecting Transverse Electric (TE) mode signals and Transverse Magnetic (TM) mode signals in the coherent input signal; and

a coherent transmitter block comprising: at least one pair of in-phase/quadrature-phase modulators in the substrate member for modulating the two portions separated from the second light into two I/Q modulation signals of a TE mode, respectively; a polarization beam rotator combiner in the substrate member for rotating one of the two I/Q modulated signals to a TM mode signal and combining the TM mode signal with the other of the two I/Q modulated signals in a TE mode to generate a coherent output signal for transmission to the coherent optical network through a polarization-independent semiconductor optical amplifier.

2. The integrated coherent transceiver of claim 1, wherein said substrate member is a silicon photonic substrate or a planar optical circuit substrate.

3. The integrated coherent transceiver of claim 1, wherein said laser diode chip comprises a plurality of surface reference points that interface with substrate reference points of a plurality of corresponding portions in a patterned surface area of said substrate member to align a first end face of said gain region with an edge stop of an integrated coupler in said substrate member to convey light generated in said gain region into said wavelength tuning section and to align a second end face of said gain region with another integrated coupler to output said laser light to said waveguide.

4. The integrated coherent transceiver of claim 3, wherein said wavelength tuning section comprises a straight waveguide coupled to at least two micro-ring resonator lines followed by a reflector section, said straight waveguide being directly coupled to said integrated coupler to receive light generated in said gain region, at least two ring resonators having slightly different radii to allow tuning of light over an extended wavelength range of the composite spectrum, and said reflector section being characterized by a reflectivity of said light of at least 90%.

5. The integrated coherent transceiver of claim 4, wherein straight portions comprise SiN material, said at least two ring resonators and said reflector portion comprise Si material.

6. The integrated coherent transceiver of claim 4, wherein said wavelength tuning section further comprises at least three thin film resistor heaters respectively placed on said substrate member and at least partially above said at least two ring resonators and said reflector section.

7. The integrated coherent transceiver of claim 6, wherein said thin film resistor heaters placed over said at least two ring resonators are configured to tune said light over an extended wavelength range of at least 1530nm to 1570nm, and said thin film resistor heaters placed over said reflector section are configured to tune a phase of said light to match a round-trip cavity lasing condition between first and second end faces of said gain region.

8. The integrated coherent transceiver of claim 1, wherein said tunable laser arrangement comprises two laser diode chips flip-chip on said substrate member to provide two active gain regions coupled to a wavelength tuning section; and a wavelength locker having three photodiodes integrated in the substrate member.

9. The integrated coherent transceiver of claim 1, wherein said first power splitter is configured in said substrate member to split said first light and said second light at an X: Y ratio in a range of 10:90 to 50: 50.

10. The integrated coherent transceiver of claim 1, wherein said second power splitter is configured to split said first light substantially equally in power.

11. The integrated coherent transceiver of claim 1, wherein said polarization beam splitter rotator comprises a rib-structured waveguide formed in said substrate member, said rib-structured waveguide configured to convert TM-mode polarization of incident light from an input port into substantially TE-type polarization, said incident light being coherent input light received from said coherent optical network.

12. The integrated coherent transceiver of claim 11, wherein said polarization beam splitter rotator comprises a biconic waveguide configured as a 50:50 splitter after said rib waveguide.

13. The integrated coherent transceiver of claim 12, wherein said polarization beam splitter rotator comprises a dual-branch waveguide coupled to said double-tapered waveguide and configured to provide an additional 90 ° phase shift to light waves propagating in one branch.

14. The integrated coherent transceiver of claim 13, wherein said polarization beam splitter rotator comprises a rectangular waveguide coupled to said double-branch waveguide and configured as a2 x 2 multimode interferometer to output TE mode polarized light to a first port and TM mode polarized light to a second port upon receiving coherent light input via an input port of said rib structure waveguide.

15. The integrated coherent transceiver of claim 1, wherein one of the at least two 90 ° hybrid receivers is configured as a TE90 ° hybrid receiver to convert a mixed optical signal into a first mixed current signal to detect a TE mode signal in the coherent input signal, the mixed optical signal combining the TE mode signal in the coherent input signal and a first TE mode local oscillator signal separated from the first light from the tunable laser device; another of the at least two 90 ° hybrid receivers is configured as a TM + 90 ° hybrid receiver to convert a mixed optical signal combining a TE mode signal rotated from the TM mode signal in the coherent input signal and a second TE mode local oscillator signal separated from the first light from the tunable laser device into a second mixed current signal to detect a TM mode signal in the coherent input signal.

16. The integrated coherent transceiver of claim 15, wherein the coherent receiver block further comprises a transimpedance amplifier (TIA) chip flip-chip mounted on the substrate member and coupled to the at least two 90 ° hybrid receivers to process the first and second hybrid current signals to convert the first and second hybrid current signals to digital signals.

17. The integrated coherent transceiver of claim 1, wherein the coherent transmitter block further comprises a driver chip flip-chip on the substrate member and configured to provide bias power and a drive signal to the at least one pair of in-phase/quadrature-phase modulators.

18. The integrated coherent transceiver of claim 1, wherein said polarization beam rotator combiner is a shaped waveguide configured in said substrate member substantially identical to said polarization beam splitter rotator having a reverse optical path.

19. The integrated coherent transceiver of claim 1, wherein each pair of in-phase/quadrature-phase modulators comprises a Mach-Zehnder delay line interferometer in each in-phase branch and an additional 90 ° phase shifter in each quadrature-phase branch.

20. The integrated coherent transceiver of claim 1, wherein said coherent transmitter block further comprises one or more optical attenuators integrated in two waveguides in said substrate member, said two waveguides being respectively coupled into two inputs of said polarization beam rotator combiner.

21. A package for an integrated coherent optical transceiver, the package comprising:

a metal housing having two side members engaged by an engaging member coupled with the base member and clamped with the cover member;

a Printed Circuit Board (PCB) disposed on the base member and having a plurality of electrical pins near a rear end of the metal housing;

the silicon photonic substrate is arranged on the PCB, and a grid array is arranged at the bottom of the silicon photonic substrate;

an input port and an output port respectively disposed at a front end of the metal housing and coupled to the silicon photonic substrate via a first optical fiber and a second optical fiber;

a tunable laser device comprising two laser diode chips coupled with a wavelength tuning section embedded in a first region of the silicon photonic substrate and configured to output laser light;

the transimpedance amplifier TIA chip is inversely installed in the second area of the silicon photonic substrate;

a driver chip flip-chip mounted in a third region of the silicon photonics substrate; and

a silicon photonic circuit formed in a fourth region of the silicon photonic substrate and configured to couple with the first optical fiber to receive a coherent input optical signal and to couple with the tunable laser device to receive a first portion of laser light as a local oscillator signal to assist the TIA chip in detecting TM and TE mode optical signals in the coherent input optical signal and to drive modulation of a second portion of the laser light using the driver chip to generate a coherent output optical signal that is output to the second optical fiber.

22. The package of claim 21, wherein the silicon photonics substrate is a silicon photonics chip including waveguides formed of silicon-related material formed in a silicon-on-insulator substrate including a plurality of electrically conductive through-silicon vias for connecting chips mounted on top of the silicon-on-insulator substrate to some grid array of the bottom.

23. The package of claim 21, wherein the two laser diode chips are configured such that p-side electrodes of the respective two gain regions face down mounted on the first region, the first region being patterned with a plurality of surface reference points, vertical stops, edge stops, and bond pads on the silicon photonics substrate; and the two laser diode chips are configured such that respective rear end faces of the two gain regions are optically aligned with the wavelength tuning section and a front end face of a first of the two gain regions outputs the laser light.

24. The package of claim 23, wherein the wavelength tuning section comprises two or more micro-ring resonator waveguides followed by a reflector waveguide, the two or more micro-ring resonator waveguides coupled to first and second ones of the two gain regions, respectively, the two or more ring resonators having slightly different radii such that light coupled from the two gain regions is reflected multiple times in the two gain regions at least 90% reflectivity and tuned over an extended wavelength range of the composite spectrum by at least one resistive heater partially covering each of the two or more micro-ring resonator waveguides.

25. The package of claim 24, wherein the tunable laser device further comprises a wavelength locker formed in the first region of the silicon photonic substrate having an input port coupled to the waveguide from the reflector portion, a monitor port separate from the input port, a first interferometric output port and a second interferometric output port separate from the two branches of the delay line interferometer waveguide, each of the monitor port, the first interferometric output port and the second interferometric output port coupled to a photodetector.

26. The package of claim 21, wherein the silicon photonic circuitry comprises a first power splitter coupled to the tunable laser device and configured to split at an X in a range from 10:90 to 50: y-ratio separates the laser into the first portion and the second portion.

27. The package of claim 21, wherein the silicon photonic circuit comprises a polarization beam splitter rotator configured to shape a silicon waveguide to receive the coherent input optical signal transmitted from the input port and to output a TE mode optical signal and a TM mode optical signal of the coherent input optical signal, the TM mode optical signal being substantially a TE mode optical signal rotated by 90 ° from a TM mode optical signal of the coherent input optical signal.

28. The package of claim 27, wherein the silicon photonic circuit comprises a second power splitter configured as a 3dB coupler to split the first portion of the laser in half as two local oscillator signals.

29. The package of claim 28, wherein the silicon photonic circuit comprises two 90 ° hybrid receivers, one 90 ° hybrid receiver configured to obtain a first hybrid optical signal and convert the first hybrid optical signal to a first hybrid current signal, the first hybrid optical signal combining the TE mode optical signal and a first of the two local oscillator signals; another 90 ° hybrid receiver is configured to obtain a second mixed optical signal that combines the TM mode optical signal and a second of the two local oscillator signals, and to convert the second mixed optical signal into a second mixed current signal.

30. The package of claim 29, wherein the TIA chip is flip-chip mounted in the second region of the silicon photonics substrate and electrically coupled to the two 90 ° hybrid receivers to process the first and second hybrid current signals into respective voltage signals.

31. The package of claim 21, wherein the silicon photonic circuit comprises two in-phase/quadrature-phase modulators, each configured with a waveguide-based Mach-Zehnder interferometer in the in-phase branch and an additional 90 ° phase shifter in the quadrature-phase branch.

32. The package of claim 31, wherein the driver chip is flip-chip mounted in the third region of the silicon photonics substrate and electrically coupled to the two in-phase/quadrature-phase modulators to provide a bias voltage and a drive signal to control 4-level I/Q modulation of two optical signals respectively through two waveguide-based Mach-Zehnder delay line interferometers.

33. The package of claim 32, wherein the silicon photonic circuit comprises a polarization beam rotator combiner coupled to the two in-phase/quadrature-phase modulators to output one of two modulated optical signals as a TE mode modulated optical signal while rotating the other of the two modulated optical signals into a TM mode modulated optical signal and combining the TE mode modulated optical signal and the TM mode modulated optical signal into a coherent modulated optical signal.

34. The package of claim 33, wherein the silicon photonic circuit further comprises one or more optical attenuators integrated to be respectively coupled with the polarization beam rotator combiner to balance optical power of the TE mode modulated optical signal with optical power of the TM mode modulated optical signal.

35. The package of claim 23, further comprising a polarization-independent semiconductor optical amplifier coupled to a polarization beam rotator combiner in the silicon photonic circuit to provide a wide range of output powers for a coherently modulated optical signal and coupled to an optical fiber to transmit the coherently modulated optical signal output to the output port as the coherent output optical signal.

36. The package of claim 21, wherein the polarization independent semiconductor optical amplifier is a chip mounted on the silicon photonic substrate.

37. The enclosure of claim 21, wherein the input port includes an optical connector receiver having a back end coupled to the first optical fiber and a front end configured to mate with a connector connected to an input optical fiber, and the output port includes an optical connector receiver having a back end coupled to the second optical fiber and a front end configured to mate with a connector connected to an output optical fiber.

38. The enclosure of claim 21, further comprising a fiber-to-silicon coupler configured to maintain the first and second optical fibers in alignment with first and second waveguides, respectively, of the silicon photonic circuit, the first waveguide leading to a polarization beam splitter rotator and the second waveguide leading to a polarization beam rotator combiner.

39. The package of claim 21, wherein each of the two 90 hybrid receivers comprises a plurality of photodetectors.

40. The package of claim 21, wherein the TIA chip and the driver chip are respectively coupled with two ASIC chips mounted on the PCB for digital signal processing.

41. The enclosure of claim 21, further comprising a pluggable feature passing through the back end of the metal housing, the pluggable feature having a plurality of electrical pins to plug the integrated coherent optical transceiver into a network system device.

42. A light engine apparatus comprising an optical coherent transceiver integrated on a semiconductor substrate member, the light engine apparatus comprising:

a substrate member including a surface region;

an optical input configured to an input fiber optic device;

an optical output configured to an output fiber optic device;

a transmit path disposed on the surface region and comprising:

a polarization-independent optical amplifier device coupled to the optical output;

a polarization beam rotator combiner arrangement coupled to the polarization-independent optical amplifier and to the optical output;

a dual polarization I/Q Mach Zehnder modulator device coupled to the polarization beam rotator combiner device and coupled to an optical output;

a driver arrangement coupled to the dual-polarization I/Q Mach Zehnder modulator arrangement and configured to drive an electrical signal to the dual-polarization I/Q Mach Zehnder modulator;

a tunable laser including a laser diode chip having a gain region with a p-side electrode thereof mounted upside down on the substrate member, the gain region being coupled with a wavelength tuning portion formed in the substrate member to tune a wavelength of laser light output from the gain region to a waveguide in the substrate member;

a first power splitter coupled to the waveguide to split the laser light into first and second light, the second light coupled to the dual-polarization I/Q Mach Zehnder modulator device;

a receiving path disposed on the surface area and comprising:

a second power splitter coupled to the first light;

a pair of 90 ° hybrid receivers, each 90 ° hybrid receiver comprising a photodetector arrangement and a hybrid mixer arrangement, the pair of 90 ° hybrid receivers respectively coupled to two outputs of a polarization beam splitter rotator in the substrate member to receive an optical input and to two outputs of the second power splitter to receive the first light from a tunable laser arrangement to assist in detecting Transverse Electric (TE) mode signals and Transverse Magnetic (TM) mode signals in a coherent input signal; and

a transimpedance amplifier coupled to each of the 90 ° hybrid receivers and to each of the photodetector devices that converts the combination of the first light and the optical input into an electrical signal for transmission using the transimpedance amplifier device; and

a hetero-integration configured to form a single silicon photonic device using the substrate member, the transmit path, and the receive path.

43. The light engine apparatus of claim 42, wherein the substrate member comprises a silicon substrate.

44. The light engine apparatus of claim 42, wherein the transimpedance amplifier is fabricated from a silicon germanium bipolar technology or a silicon CMOS technology or an indium phosphide technology or a gallium arsenide containing technology.

45. The light engine apparatus of claim 42, wherein the light engine apparatus is coupled to a primary substrate member, the primary substrate member comprising:

the light engine device;

a digital signal processing device coupled to the light engine device;

a power supply coupled to the light engine apparatus and the digital signal processing apparatus;

a microcontroller device coupled to the light engine device to provide one or more controls to the light engine device using one or more control signals;

electrical inputs and outputs configured to said light engine means, said digital signal processing means, said power supply and microcontroller means; and

an electromechanical configuration comprising said light engine means, said digital signal processing means, said power supply, said microcontroller means, and said electrical inputs and outputs configured to said light engine means, said digital signal processing means, said power supply and said microcontroller means.

46. The light engine apparatus of claim 45, wherein the light engine apparatus and the primary substrate member are configured as pluggable devices.

47. The light engine apparatus of claim 45, wherein the light engine apparatus and the primary substrate member are configured on a system board member.

48. The light engine apparatus of claim 47, wherein the system board component is disposed in a switching system device spatially disposed in a data center.

49. The light engine apparatus of claim 48, wherein the data center is configured for a social networking platform, an electronic commerce platform, an artificial intelligence platform, or a human tracking platform.

50. The light engine apparatus of claim 48, wherein the data center is coupled to a plurality of data centers spatially located over an entire geographic area.

51. The light engine apparatus of claim 48, wherein the data center is owned by a commercial company or a government entity.

52. The light engine apparatus of claim 45, wherein the digital signal processing apparatus comprises a host interface to a switching apparatus and a line interface to the light engine apparatus.

53. The light engine apparatus of claim 47, wherein the primary substrate member comprises an electrical interface to the system substrate member, an optical interface to the system substrate member, and a mechanical interface to the system substrate member, and the primary substrate member is thermally configured onto the system substrate member using an attachment device, using a thermal interface coupled to the attachment device.

Technical Field

The present invention relates to an optical communication technology. More particularly, the present invention provides a compact integrated coherent transceiver based on a silicon photonics platform, a method of forming the same, and a system having the same.

Background

The use of communication networks has proliferated over the past decades. In the early internet, popular applications were limited to email, bulletin boards, primarily information and text-based web browsing, and the amount of data transferred was typically relatively small. Today, the internet and mobile applications require a large amount of bandwidth to transfer photos, videos, music, and other multimedia files. For example, social networks like facebooks handle over 500TB of data per day. Because of the so high demands for data and data transmission, there is a need to improve existing data communication systems to meet these demands.

Broadband DWDM (dense wavelength division multiplexing) optical transmission at 40Gbit/s and 100Gbit/s data rates over existing single-mode fibers is the target of next generation fiber optic communication networks. For many applications, such as broadband DWDM communication and wavelength-controlled light detection and ranging (LIDAR) sensing, a widely tunable laser at the chip level has attracted interest. Recently, optical components are integrated on silicon (Si) substrates to fabricate large-scale photonic integrated circuits that coexist with microelectronic chips. It has been demonstrated that the entire photonic assembly, including filters, (de) multiplexers, splitters, modulators and photodetectors, is primarily on a silicon-on-insulator (SOI) platform. SOI platforms are particularly well suited for the 1300nm and 1550nm standard DWDM communications bands because of silicon (n 3.48) and its oxide SiO₂(n-1.44) are all transparent and form a high index, high confinement waveguide ideally suited for use in medium to high integrated Planar Integrated Circuits (PICs).

Coherent fiber optic communication was extensively studied in the 1980 s, mainly because the high sensitivity of coherent receivers can extend the unrepeated transmission distance; however, after rapid development of high-capacity Wavelength Division Multiplexing (WDM) systems using erbium-doped fiber amplifiers (EDFAs), research and development thereof have been interrupted for nearly 20 years. Recently, the demonstration of digital carrier phase estimation in coherent receivers has again stimulated widespread interest in coherent optical communications. The fact is that digital coherent receivers enable us to employ a variety of spectrally efficient modulation formats, such as M-Phase Shift Keying (PSK) and Quadrature Amplitude Modulation (QAM), without relying on a rather complex optical phase-locked loop. In addition, since the phase information is preserved after detection, we can implement electrical post-processing functions in the digital domain, such as dispersion compensation and polarization mode dispersion compensation. These advantages of coherent receivers have great potential for innovating existing optical communication systems.

The coherent transmitter has TE and TM paths. However, silicon photonics chips actually only operate in the TE-only configuration. There are technical challenges to fabricating polarization independent or wavelength tunable passive and active components, and integrating these components to form coherent optical transceivers in compact silicon photonic platforms. Accordingly, there is a need for improved techniques and methods of forming integrated compact coherent transceivers.

Disclosure of Invention

The present invention relates to optical communication technology. More specifically, the present invention provides an integrated compact coherent transceiver in a silicon photonics platform. By way of example only, the present invention discloses: a coherent transmitter block comprising a polarization independent Semiconductor Optical Amplifier (SOA) coupled to a driver electronics chip via a Polarization Beam Rotator Combiner (PBRC), the driver electronics chip having in-phase and quadrature-phase modulation of a broadband signal from a separately packaged broadband tunable laser, the laser having a silicon photonic tuning section; and a coherent receiver block comprising a polarization hybrid receiver that converts the TE polarized optical signal split by the Polarization Beam Splitter Rotator (PBSR) to an electrical signal for a transimpedance amplifier (TIA) electronics chip; and methods of integrating these components in a compact silicon photonic platform to form coherent transceivers for broadband DWDM optical communications, although other applications are also possible.

In modern electrical interconnect systems, high speed serial links have replaced parallel data buses, and serial link speeds are rapidly increasing due to advances in CMOS technology. Following moore's law, internet bandwidth almost doubles every two years. Moore's law will end in the next decade. Standard CMOS silicon transistors will stop scaling around 5 nm. Internet bandwidth will steadily increase due to process expansion. The internet and mobile applications continue to require a large amount of bandwidth to transfer photos, videos, music, and other multimedia files. This disclosure describes techniques and methods to increase communication bandwidth beyond moore's law.

With the increase of transmission capacity of WDM systems, coherent technology has attracted extensive attention after 2000. The motivation was to develop methods to meet the ever-increasing bandwidth demands through multi-level modulation formats based on coherent technologies. The first step of the renaming coherent optical communication study was triggered by Quadrature Phase Shift Keying (QPSK) modulation/demodulation experiments with optical in-phase and quadrature (IQ) modulation (IQM) and optical delay detection functions. In such a scheme, we can double the bit rate while maintaining the symbol rate, and a 40Gb/s differential qpsk (dqpsk) system has been put into practical use. The coherent transmitter has Transverse Electric (TE) mode and Transverse Magnetic (TM) mode paths. Silicon photonics chips actually only operate in TE-only configurations. The signal has both TE mode and TM mode portions. To enable the integration of coherent transceivers based on silicon photonics, we need to have at least the following two components on a silicon photonics chip: 1) a Polarization Beam Rotator Combiner (PBRC) integrated in the coherent transmitter with a polarization independent Semiconductor Optical Amplifier (SOA) and a driver; and 2) a Polarization Beam Splitter Rotator (PBSR) integrated with electronic devices such as a transimpedance amplifier (TIA) in a coherent receiver, and integrating the coherent transmitter and receiver with a tunable laser provided in a flip chip.

In an embodiment, the present invention provides a tunable laser device based on silicon photons. The tunable laser apparatus includes: a substrate configured with a patterned region comprising one or more vertical stops; an edge stop facing in a first direction; a first alignment feature formed in the patterned region along a first direction; and a bonding pad disposed between the vertical stoppers (stoppers). The tunable laser device further includes an integrated coupler built into the substrate at the edge stop. Further, the tunable laser apparatus includes: a laser diode chip including a gain region covered by a P-type electrode; and a second alignment feature formed outside the P-type electrode, the laser diode chip flipped to rest on the one or more vertical stops, wherein the P-type electrode is attached to the bond pad and the gain region is coupled to the integrated coupler. Furthermore, the tunable laser device comprises a tuning filter fabricated in the substrate and coupled to the integrated coupler via the wire waveguide.

In a specific embodiment, the present invention provides a coherent transceiver integrated on a silicon photonics substrate. A coherent transceiver includes a substrate member and a tunable laser arrangement including a laser diode chip having a gain region with a p-side electrode flipped down and mounted on the substrate member. The gain region is coupled with a wavelength tuning section formed in the substrate member to tune a wavelength of laser light output from the gain region to the waveguide in the substrate member. The coherent transceiver also includes a first power splitter coupled to the waveguide to split the laser light into first and second light. In addition, the coherent transceiver includes a coherent receiver block including at least two 90 ° hybrid receivers respectively coupled to two outputs of the polarization beam splitter rotator in the substrate member to receive the coherent input signal from the coherent optical network. The coherent transceiver is further configured to have two 90 ° hybrid receivers coupled to two outputs of the second power splitter to receive two local oscillator signals split from the first light to assist in detecting Transverse Electric (TE) mode signals and Transverse Magnetic (TM) mode signals in the coherent input signal. Further, the coherent transceiver includes a coherent transmitter block including at least one pair of in-phase/quadrature-phase modulators in the substrate member, modulating the two parts separated from the second light into two I/Q modulated signals in TE mode, respectively; a polarization beam rotator combiner is included in the substrate member to rotate one of the two I/Q modulated signals into a TM mode signal and combine it with the other of the two I/Q modulated signals in a TE mode to generate a coherent output signal that is transmitted through the polarization independent semiconductor optical amplifier to the coherent optical network.

In another embodiment, the present invention provides a package for an integrated coherent optical transceiver. The package includes: and a metal housing having two side members engaged by an engaging member coupled with the base member and clamped by the cover member. The package further includes: a Printed Circuit Board (PCB) disposed on the base member, having a plurality of electrical pins near a rear end of the metal housing; and a silicon photonic substrate mounted on the PCB and having a grid array at the bottom thereof. In addition, the package includes a coherent transceiver chip integrated on the silicon photonics substrate, the chip including an input port and an output port disposed at a front end of the metal housing and coupled to the silicon photonics substrate via a first optical fiber and a second optical fiber, respectively. The coherent transceiver chip also includes a tunable laser arrangement including two laser diode chips coupled with a wavelength tuning section embedded in the first region of the silicon photonic substrate and configured to output laser light. Further, the coherent transceiver chip includes a transimpedance amplifier (TIA) chip flip-chip mounted on the second region of the silicon photonics substrate and a driver chip flip-chip mounted on the third region of the silicon photonics substrate. Further, the coherent transceiver chip includes a silicon photonic circuit formed in a fourth region of the silicon photonic substrate. The silicon photonic circuit is configured to be coupled with the first optical fiber to receive the coherent input optical signal and configured to be coupled with the tunable laser device to receive a first portion of the laser as a local oscillator signal to assist the TIA chip in detecting the TM mode and TE mode optical signals in the coherent input optical signal. The silicon photonic circuit is further configured to drive modulation of a second portion of the laser using the driver chip to generate a coherent output optical signal that is output to the second optical fiber.

In another embodiment, the invention provides a light engine apparatus comprising an optical coherent transceiver integrated on a semiconductor substrate member. The light engine device comprises: a substrate member including a surface region. The light engine apparatus further comprises: an optical input configured to an input fiber optic device and an optical output configured to an output fiber optic device. In addition, the light engine arrangement includes an emission path disposed on the surface area. The transmit path includes a polarization-independent optical amplifier device coupled to the optical output. The transmit path also includes a polarization beam rotator combiner arrangement coupled to the polarization-independent optical amplifier and to the optical output. The transmit path further includes a dual polarization I/Q Mach Zehnder modulator device coupled to the polarization beam rotator combiner device and coupled to the optical output. The transmit path further includes a driver arrangement coupled to the dual-polarization I/Q Mach Zehnder modulator arrangement and configured to drive an electrical signal to the dual-polarization I/Q Mach Zehnder modulator. In addition, the emission path includes a tunable laser including a laser diode chip having a gain region with a p-face electrode flipped down and mounted on a substrate member. The gain region is coupled with a wavelength tuning portion formed in the substrate member to tune a wavelength of laser light output from the gain region to the waveguide in the substrate member. Further, the transmit path includes a first power splitter coupled to the waveguide to split the laser light into first and second light. The second light is coupled to a dual polarization I/Q Mach Zehnder modulator device. In addition, the light engine apparatus further includes a receiving path disposed on the surface area. The receive path includes a second power splitter coupled to the first light. The receive path also includes a pair of 90 ° hybrid receivers. Each of the pair of 90 ° hybrid receivers includes a photodetector arrangement and a hybrid mixer arrangement, the pair of 90 ° hybrid receivers respectively coupled to two outputs of the polarization beam splitter rotator in the substrate member to receive the optical input and to two outputs of the second power splitter to receive the first light from the tunable laser arrangement to assist in detecting Transverse Electric (TE) mode signals and Transverse Magnetic (TM) mode signals in the coherent input signal. Further, the receive path includes a transimpedance amplifier coupled to each 90 ° hybrid receiver and to each photodetector device, the photodetector devices converting the combination of the first light and the optical input into an electrical signal for transmission using the transimpedance amplifier devices. The light engine apparatus also includes a heterogeneous integration configured to form a single silicon photonic device using the substrate member, the emission path, and the reception path.

The present invention achieves these and other advantages in the context of known waveguide laser modulation techniques. A further understanding of the nature and advantages of the present invention, however, may be realized by reference to the latter half of the specification and the drawings.

Drawings

The following drawings are merely examples, which should not unduly limit the scope of the claims herein. One of ordinary skill in the art would recognize many other variations, modifications, and alternatives. It is also understood that the examples and embodiments described herein are for illustrative purposes only and that various modifications or changes in light thereof will be suggested to persons skilled in the art and are to be included within the spirit and purview of this process and scope of the appended claims.

FIG. 1 is a simplified block diagram of a coherent optical transceiver according to an embodiment of the present invention.

FIG. 2A is a top view of a waveguide-based polarization beam splitter-rotator (PBSR) or polarization beam rotator-combiner (PBRC) according to an embodiment of the present invention.

Fig. 2B is a cross-sectional view along the AA' plane of the waveguide-based PBSR or PBRC of fig. 2A, in accordance with an embodiment of the present invention.

Fig. 2C is a cross-sectional view along the BB' plane of the waveguide-based PBSR or PBRC of fig. 2A, in accordance with an embodiment of the present invention.

Fig. 2D is a cross-sectional view along the CC' plane of the waveguide-based PBSR or PBRC of fig. 2A, in accordance with an embodiment of the present invention.

Fig. 3 is a simplified diagram of a silicon photonic tunable laser apparatus according to an embodiment of the present invention.

Fig. 4 is a schematic diagram illustrating a perspective view of a laser diode chip flip-chip bonded to a silicon photonics substrate in accordance with an embodiment of the present invention.

Fig. 5 is an exemplary diagram of a wavelength tuning diagram of a silicon photonic tunable laser according to an embodiment of the present invention.

Fig. 6 is a simplified diagram of a silicon photonic tunable laser according to another embodiment of the present invention.

Fig. 7 is a flow chart of a method for tuning the wavelength of the laser output of a silicon photonic tunable laser apparatus according to an embodiment of the present invention.

Fig. 8 is an exemplary diagram of two superimposed transmission spectra of respective two ring resonators of tunable filters having different radii in a silicon photonic tunable laser apparatus according to an embodiment of the present invention.

FIG. 9 is an exemplary diagram of reflectivity spectra of reflectors coupled to two ring resonators of a tunable filter according to an embodiment of the present invention.

Figure 10 is a simplified block diagram of a tunable filter including two ring resonators, a reflector plus a phase shifter in a vernier ring reflector configuration in accordance with an embodiment of the present invention.

Fig. 11 is an exemplary diagram of two composite spectra corresponding to wavelengths tuned from 1555nm to 1535nm and corresponding gain distributions tuned from 1530nm to 1570nm, respectively, by tuning a tunable filter in a vernier ring reflector configuration, according to an embodiment of the present invention.

Fig. 12 is an exemplary diagram of a laser spectrum output by a silicon photonic tunable laser apparatus with a laser wavelength tuned from 1555nm to 1535nm according to an embodiment of the present invention.

FIG. 13 is a schematic diagram of three types of SiN based integrated couplers in Si waveguides, according to some embodiments of the invention.

Fig. 14A is an exemplary diagram of a relationship between coupling loss and lateral misalignment of an integrated coupler coupled between a tunable filter and a laser diode chip, according to an embodiment of the invention.

Fig. 14B is an exemplary diagram of a relationship between coupling loss and vertical misalignment of an integrated coupler coupled between a tunable filter and a laser diode chip, according to an embodiment of the invention.

Figure 15A is a perspective view of an integrated coherent optical transceiver on a silicon photonics substrate in accordance with an embodiment of the present invention.

Figure 15B is a side view of an integrated coherent optical transceiver on the silicon photonics substrate of figure 15A, in accordance with embodiments of the present invention.

Fig. 16A is a schematic diagram of an open package of an integrated coherent optical transceiver according to an embodiment of the present invention.

Fig. 16B is a schematic diagram of a closed package of the integrated coherent optical transceiver of fig. 16A, in accordance with an embodiment of the present invention.

Detailed Description

The present invention relates to optical communication technology. More particularly, the present invention provides an integrated compact coherent transceiver on a silicon photonics platform. By way of example only, the present invention discloses: a coherent transmitter block comprising a polarization independent Semiconductor Optical Amplifier (SOA) coupled via a Polarization Beam Rotator Combiner (PBRC) to a driver electronics chip and an independently packaged broadband tunable laser with a silicon photonic tuning section; a coherent receiver block comprising a polarization-hybrid receiver via which a Polarization Beam Splitter Rotator (PBSR) is coupled to a transimpedance amplifier (TIA) electronics chip; and a method of integrating these components in a compact silicon optical sub-platform to form a coherent transceiver for broadband DWDM optical communications, although other applications are also possible.

The following description is presented to enable one of ordinary skill in the art to make and use the invention and is included in the context of a particular application. Various modifications in different applications and uses will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to a wide range of embodiments. Thus, the present invention is not intended to be limited to the embodiments shown, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

In the following detailed description, numerous specific details are set forth in order to provide a more thorough understanding of the present invention. It will be apparent, however, to one skilled in the art that the present invention may be practiced without limitation to these specific details. In other instances, well-known structures and devices are shown in block diagram form, rather than in detail, in order to avoid obscuring the present invention.

The reader's attention is directed to all papers and documents which are filed concurrently with this specification and which are open to public inspection with this specification, and the contents of all such papers and documents are incorporated herein by reference. All the features disclosed in this specification (including any accompanying claims, abstract and drawings) may be replaced by alternative features serving the same, equivalent or similar purpose, unless expressly stated otherwise. Thus, unless expressly stated otherwise, each feature disclosed is one example only of a generic series of equivalent or similar features.

Furthermore, any element in the claims that does not explicitly specify a "means" or a "step" for performing a particular function is not to be construed as a "means" or "step" clause as defined in section 6 of 35u.s.c. section 112. In particular, the use of "step" or "action" in the claims herein is not intended to invoke the provisions of section 6 of section 112 of 35u.s.c.

Note that labels left, right, front, back, top, bottom, forward, reverse, clockwise, and counterclockwise, if used, are for convenience only and are not meant to implement any particular fixed orientation. Rather, they are intended to reflect the relative position and/or orientation between different parts of the object.

In one aspect, the present disclosure provides a compact integrated coherent transceiver based on a silicon photonics platform. With the increase of data transmission capacity in WDM systems, in recent years, coherent techniques with polarized optical signals have received increasing attention with the motivation to use multi-level modulation formats to meet the ever-increasing bandwidth demands. For example, a digital signal transmission/reception scheme has been developed for a coherent transmission system supported by quadrature psk (qpsk) modulation/demodulation featuring optical in-phase and quadrature (I/Q) modulation and optical delay detection. In this scheme, one symbol carries two bits by using a four-point constellation on the complex plane, and thus, while maintaining the symbol rate or the bit rate even if the spectral width is halved, the bit rate is doubled, thereby realizing a large capacity of 100Gbit/s and over 100Gbit/s per channel. Optically coherent I/Q modulation can be realized in parallel by means of a push-pull modulator of the Mach-zehnder (mz) type, giving a pi/2 phase shift between the two. The I/Q components of the optical carrier are independently modulated by a coherent I/Q modulator to implement any type of modulation format.

FIG. 1 shows a simplified block diagram of an integrated coherent optical transceiver according to an embodiment of the present invention. This diagram is merely an example, which should not unduly limit the scope of the claims. One of ordinary skill in the art would recognize many variations, alternatives, and modifications. As shown, the integrated coherent optical transceiver is configured to integrate a silicon-photon based tunable laser 1000 and coherent transmitter block 2000 and coherent receiver block 3000 on a single silicon photonic substrate 100. Optionally, the tunable laser is a broadband laser source whose output optical signal is tunable over the entire C-band or O-band. Wavelength tuning can be achieved using a silicon photonic tuning section that includes a heater-tuned micro-ring resonator filter built into the silicon photonic substrate 100, while a laser diode chip with an InP gain region and p-side down flip is mounted on the silicon photonic substrate 100. Specifically, the laser wavelength can be tuned by the silicon photonic tuning section and the waveguide-based wavelength locker to provide a clear transmission spectrum for each of all ITU channels in the C-band for DWDM communications. More details can be found in the description of fig. 3-14A and 14B of this specification. Alternatively, the laser light is output from an InP gain region coupled via an integrated coupler to a waveguide (formed in the same silicon photonic substrate 100). The waveguide carries laser light that serves as a local oscillator source for the coherent receiver 3000 to detect the incoming coherent optical signal and also as a light source for generating an I/Q modulated coherent signal that is transmitted by the coherent transmitter 2000.

Optionally, although they are not explicitly labeled in FIG. 1, the integrated coherent optical transceiver comprises a plurality of silicon waveguides respectively disposed in a silicon photonic substrate 100 for connecting a plurality of different silicon photonic components, the components comprising a power splitter, a polarization beam splitter and rotator, a polarization beam rotator and combiner, a phase shifter, a power attenuator, or a portion of an optical modulator. Alternatively, the silicon waveguide has a regular rectangular wire shape with a fixed width and height. Optionally, the height is selected based on the use of a standard 220nm silicon-on-insulator (SOI) substrate in its formation process. Optionally, the silicon waveguide has a width of about 300nm to 500 nm. Alternatively, the silicon waveguide has an alternative shape structure, depending on the particular functional application, such as a rib structure having multiple height steps, a tapered structure having varying widths along its length, or multiple branches joined at different cross-sectional planes having different widths and spacings. Alternatively, some of the silicon photonic components described above are also the silicon waveguides themselves monolithically formed in the same manufacturing process used to fabricate the silicon photonic substrate 100 for the integration of coherent optical transceivers.

For subminiature silicon waveguides of several hundred nanometers in width (parallel to the substrate) and height (perpendicular to the substrate) used in compact silicon photonic modules, they typically exhibit very strong polarization dependence (typical for telecommunications) for transmitted light with infrared wavelengths, such that the transmission loss for Transverse Electric (TE) mode polarization (parallel to the substrate) is much smaller than the transmission loss for Transverse Magnetic (TM) mode polarization (orthogonal to the substrate). Thus, typical silicon photonic devices are only suitable for the TE mode. Optionally, the output light of the tunable laser 1000 polarized in the Transverse Electric (TE) mode is split between the transmitter block 2000 and the receiver block 3000 in an optimal ratio. In the transmitter block 3000, light from the tunable laser 1000 at a wavelength selected in a wide band by the tunable filter section is first divided into TE mode light and TM x mode (still TE mode) light, both of which are optically I/Q modulated. The TE mode light becomes a TE mode signal. The TM-mode light is then polarization rotated to form a Transverse Magnetic (TM) mode signal. The TE mode signal and the TM mode signal are then combined into a coherent output signal for the transceiver at the selected wavelength. In the receiver block 3000, the optical signal (TE mode) from the tunable laser 1000 is used as a local oscillator at the wavelength selected by the tunable filter section for detecting the incoming coherent input signal.

Referring to fig. 1, the output of tunable laser 1000 is essentially TE mode laser light that is first split into two parts, first and second light, respectively, by power splitter 1001 in an X: Y ratio. The first light of the X-proportion of the laser power is delivered to the coherent receiver block 3000 and the second light of the Y-proportion of the laser is sent to the coherent transmitter block 2000. X: the Y ratio may be altered or optimized based on the particular system operating conditions. Alternatively, X is set in the range of 10% to 50%. For the first light coupled into the coherent receiver block 3000, it is further split into two 50% portions, a third light and a fourth light, by the power splitter 3001. The third light is loaded into the TE90 ° hybrid receiver 3200 and the fourth light is loaded into the TM x 90 ° hybrid receiver 3300 for aiding in the detection of TE mode/TM mode signals, respectively, of the input optical signal received by the coherent optical transceiver via the input port (optical ingress).

For the second light coupled into the coherent emitter block 2000, it is used as the original light source to generate a coherent optical signal to be sent out from the output port. Alternatively, the second light may be used as TE mode polarized light and tuned to any wavelength in a broadband such as a C-band or an O-band designated for telecommunication. In order to be used as a coherent optical signal with mixed polarization modes, it is necessary to generate the TM mode polarization part of the second light. The polarization portions of both the TE mode and the TM mode are modulated by an optical coherence modulator. Alternatively, optical coherent I/Q modulators based on silicon or silicon nitride or similar material delay line interferometers integrated in a silicon photonic substrate have been developed that have polarization compensation at selected wavelengths, for example, as shown in U.S. patent No. 10031289 assigned to Inphi corporation.

As shown in fig. 1, the coherent transmitter block 2000 and the coherent receiver block 3000 of the integrated coherent optical transceiver each have a TE mode path and a TM mode path to provide or detect coherent light with mixed polarizations in a polarization independent communication system. However, silicon photonic circuits including Si-based waveguide linear modulators operate substantially in TE-only mode configurations. To process coherent optical signals with TE and TM mode portions, a silicon-photon based coherent transceiver requires at least 1) a Polarization Beam Rotator Combiner (PBRC) integrated with a polarization independent Semiconductor Optical Amplifier (SOA) at the output port (optical egress) of the transmitter block to output coherent optical signals with TE and TM modes; and 2) a Polarization Beam Splitter Rotator (PBSR) for splitting an input coherent optical signal into a TE mode portion and a TM mode portion and then rotating the TM mode portion to the TE mode before coupling to the optical hybrid detector.

Conventional PBSR are either sensitive to wavelength such that it is not suitable for broadband operation, or are based on prisms that are difficult to make into ultra-compact sizes. Referring to U.S. patent No. 9915781, assigned to Inphi corporation, compact PBSRs based on Photonic Integrated Circuits (PICs) have been developed that have a combination of features such as compact size, high extinction ratio, low insertion loss, wide band range, stability, simple structure, and high manufacturing tolerances. Specifically, as shown in FIG. 2A, a top view of a waveguide-based polarizing beamsplitter-rotator is shown. The PBSR 16 comprises a monolithic, monolithic silicon planar waveguide that includes a plurality of shaped sections formed through a standard 220nm silicon layer of a silicon-on-insulator (SOI) substrate. The first part is a rib-structured transducer, which in fig. 2A and 2B features a top layer 1602 overlying a bottom layer 1601, the bottom layer 1601 extending in a length direction through a length L₁From the input port 1600 to the junction plane AA' and through a length L₂From the joining plane to the first cross-sectional plane 1610. The top layer 1602 is narrower than the bottom layer 1601, except that they have a first common width W at the input port 1600₀And a second common width W at the first cross-sectional plane 1610₁Both layers being over the first length L₁And the entire second length L₂And (c) an upper change. GetDepending on the wavelength range of the coherent optical signal, a specific length-width combination of both the top layer 102 and the bottom layer 1601 is configured to provide polarization mode conversion from TM mode to TE mode for transmitting coherent light waves.

A thickness h ═ h on the oxide layer_t+h_bThe 220nm silicon layer is patterned into a rib structure waveguide and after being part of the overall process of forming the PBSR 16, in a blanket process, the thickness h is applied_tIs formed to cover the top layer 1602 at a thickness h_bOver the bottom layer 1601. In a specific embodiment, the converter is configured to process light waves of broadband wavelengths, for example, the O-band in the range of 1270nm to 1330nm or the C-band of about 1530nm to about 1560nm (the rib structures are slightly different in size). In addition, the width W of the top layer 1602 at the joint plane is made_tIs greater than the first common width W₀Making the width W of the bottom layer 1601 at the joint plane_bGreater than the width W of the top layer 1602_tBut less than the second common width W₁And the first length L is made₁Is less than the second length L₂. After fine tuning of the length-width combination (standard height of 220nm) in the above configuration, the rib structured waveguide can be used as the desired polarization mode converter. For input light having a mixed TM mode and TE mode input via the input port 1600, when the input light travels to the first cross-sectional plane 1610, the TM mode is substantially converted into a first-order transverse electric (TE1) mode, and the TE mode is substantially converted into a zero-order transverse electric (TE0) mode. Specifically, the TE1 mode includes two sub-modes, out-of-phase TE1₁Sub-mode and in-phase TE1₂And (4) sub-mode. The TE0 mode is only a single phase mode.

Referring to fig. 2A, the second, shaped portion of the PBSR 16 includes a splitter 1612, the splitter 1612 directly coupled to the first cross-sectional plane of the converter as part of a monolithic planar silicon waveguide formed from the 220nm silicon layer of the SOI substrate. Fig. 2C is a cross-sectional view of the waveguide-based PBSR 10 along the BB' plane according to an embodiment of the present invention. Referring to fig. 2C and 2A, splitter 1612 is a planar waveguide having a height h of the silicon layer of 220nm, extending lengthwise from first cross-sectional plane 1610 to second cross-sectional plane 1620. A first cross-sectional plane 1610 passes throughInput light transmitted through the converter. The second cross-sectional plane 1620 includes the first port 1701 and the second port 1702, the first port 1701 and the second port 1702 being located near two opposite edges, respectively, and being spaced apart from each other by a gap W_g. In an embodiment, the splitter 1612 is designed to split the input light received at the first cross-sectional plane 1610 substantially uniformly into a first wave at the first port 1701 and a second wave at the second port 1702.

Referring again to fig. 2A, the third shaped portion of PBSR 16 includes phase shifter waveguides coupled to or naturally extending from first port 1701 and second port 1702 at a second intermediate cross-sectional plane 1620. The phase shifter waveguide comprises a first waveguide arm 121 coupled to the first port 1201 and a second waveguide arm 122 coupled to the second port 1202, both having the same height h of the 220nm silicon layer. The first waveguide arm 1621 extends lengthwise to a third port 1801 of the third cross-sectional plane 1630, and the second waveguide arm 1622 extends lengthwise separately to a fourth port 1802 of the third cross-sectional plane 1630. In an embodiment, the first waveguide arm 1621 is configured to receive the first wave from the first port 1701 and pass the first wave through at least the length L₆Toward the third port 1801 while keeping the first wave at the third port 1801 in phase with respect to the wave at the first port 1701. The second waveguide arm 1622 is configured to receive the second wave from the second port 1702 and pass the second wave through the same length L₆While adding a phase shift to the second wave at the fourth port 1802 relative to the wave at the second port 1702.

Fig. 2D is a cross-sectional view of the waveguide-based PBSR 16 of fig. 2A along the CC' plane, in accordance with an embodiment of the present invention. Referring to fig. 2A and 2D, the first waveguide arm 1621 of the phase shifter includes at least a length L₆And a first arm width W_1aIs connected between the first port 1701 and the third port 1801, and the second waveguide arm 1622 of the phase shifter comprises at least a length L₆With a triangular portion connected between the second port 1702 and the fourth port 1802The columns are joined together. Second waveguide arm 1622 has a varying second arm width W_2aThe second arm width W_2aFirst arm width W from one end_1aIncreasing to a maximum at the apex of the triangular portion and then decreasing again to a first arm width W at the other end_1a. And length L in first waveguide arm 1621₆Associated constant width W_1aEffectively keeping the first wave traveling through the first waveguide arm 1621 to reach the third port 1801 at the third cross-sectional plane 1630 in phase. At the same time, the length L in the second waveguide arm 1622 may be adjusted₆Associated variation width W_2aTo provide a desired phase delay to a second wave traveling independently through the second waveguide arm 1622 to reach the fourth port 1802 at the third cross-sectional plane 1630. In a particular configuration, the maximum W_2aIs set slightly smaller than the first arm width W_1aAnd length L, and₆not greater than 11 μm, thereby creating a phase delay of (1/2) π for the second wave passing through the second waveguide arm 1622. Alternatively, by slightly reducing the maximum value W_2aAnd increasing the length L₆A phase delay of (3/2) pi may be generated for the second wave passing through the second waveguide arm 1622. In principle, a phase shift of (π/2+ n π) can be generated for any integer that is n, although the effective phase value is limited to 2 π.

Referring again to FIG. 2A, the fourth shaped section of the PBSR 16 includes a2 × 2MMI coupler 1632 that extends as a planar waveguide having the same height h of the 220nm silicon layer, naturally from the third port 1801 and the fourth port 1802 at the third cross-sectional plane 1630 to an output plane 1640 having the first output port 1901 and the second output port 1902. from the input port 1600 to the fourth cross-sectional plane 1640, the total length of the PBSR 16 is less than 100 μm, thus forming a compact device suitable for use in a highly integrated silicon photonic communication system.2 2 × 2MMI coupler 1632 is characterized by a length L measured from the third cross-sectional plane 1630 to the output plane 1640₇And width W₂Is rectangular. The first output port 1401 is distant from the center line of the rectangular planar waveguide by a distance W in the length direction_pIs aligned with the third port 1801 at the bar position. First output port 1901 phaseThe second and fourth ports 1902, 1802 are in mirror symmetry with respect to the first and third ports 1901, 1801 respectively, but the second output port 1902 is in a crossed position with respect to the third port 1801. this configuration of the 2 × 2MMI coupler 1632 causes general interference of the optical wave coupled via the third and fourth ports 1801, 1802 and outputs a first output light in the TE0 mode to the first output port 1901 and a second output light in the TE0 mode to the second output port 1902. depending on the specific polarization mode and the phase difference of the first wave at the third port 1801 and the second wave at the fourth port 1802, optionally, the first output light may originate exclusively from the TM mode and the second output light exclusively from the TE mode.

Referring back to fig. 1, for the coherent receiver block 3000, the input coherent optical signal R has a mixed TE/TM mode part in I/Q modulation. PBSR 3100 is for receiving an input optical signal R and following the polarization splitting/rotating function described above, splitting the TE mode partial signal R in TE polarization_EOutputs to the first waveguide, and also polarizes the TM mode part R with TE_MThe output is branched to TM compatible with silicon photonics chips that operate only in TE mode. Then the TE mode partial signal R in the TE branch is divided_ELoaded into a TE90 ° hybrid receiver 3200 that also receives as a second input a TE-mode Local Oscillator (LO) signal a split from the tunable laser 1000 (fig. 1.) the TE90 ° hybrid receiver 3200 produces four outputs 1/2 × (R/Q demodulation) through preferred I/Q demodulation_E+A)、1/2×(R_E–A)、1/2×(R_E+ jA) and 1/2 × (R)_EJoa), into a transimpedance amplifier (TIA) chip 3400, where thisThe optical signals are converted into two current signals I by a balanced photodetector_IAnd I_Q. Further, the TIA chip includes an analog-to-digital converter to convert the current signal into a digital signal that can be processed in a Digital Signal Processor (DSP) (not explicitly shown), and the TE mode partial signal of the input coherent light can be specifically detected. Similarly, the TE mode partial signal R in the TM branch_MLoaded into the TM x 90 ° hybrid receiver 3300, which TM x 90 ° hybrid receiver 3300 also receives as a second input the LO signal a in the TE mode split from the tunable laser 1000. Further, the output of the TM × 90 ° hybrid receiver 3300 is sent to the TIA chip 3400, and in the TIA chip 3400, the TM mode partial signal of the input coherent light can be specifically detected via I/Q demodulation. Optionally, TIA chip 3400 is a flip chip mounted on a silicon photonics substrate 100 shared with a silicon photonics chip comprising PBSR 3100 and power splitter 3001.

Referring again to fig. 1, the coherent transmitter block 2000 receives Y-ratio light of an unmodulated TE mode split from the tunable laser 1000 and requires optical I/Q modulation for coherent communication. In this embodiment, the coherent transmitter block 2000 includes a driver chip 2600, the driver chip 2600 configured to provide a bias voltage and a digital transmit electrical signal to the optical modulator to modulate the input light from the tunable laser 1000. The driver chip 2600 (e.g., including a serializer, a 4-level encoder, a 2-bit digital-to-analog converter) is provided in a flip chip mounted on the same silicon photonics substrate 100. Alternatively, the driver chip 2600 and the TIA chip 3400 may be integrated into a single chip. In an embodiment, the coherent I/Q modulator is based on a delay line interferometer made of silicon or silicon nitride or similar material integrated in a silicon photonics chip that shares the same silicon photonics substrate 100 with the coherent receiver block 3000. The Y-ratio light from the TE mode of the tunable laser 1000 is split into a first input light in the TE branch 2501 and a second input light in the TM branch 2502. Here, the splitting of the Y-ratio light is done via a 50:50 power splitter (not explicitly shown) while retaining its TE polarization in either branch. Each of the first input light and the second input light is coupled into an I/Q modulator. In this embodiment, the first I/Q modulator is configured with four linear waveguide arms with different phase delays to receive four equally divided portions of the first input light through three power splitters in two stages. The first pair of arms form an in-phase (I) branch in a Mach-Zehnder modulation configuration that produces a first output having an in-phase modulation component for a first input light entering the TE branch 2501. The second pair of arms also forms a quadrature phase (Q) branch in a Mach-Zehnder modulation configuration plus a 90 ° phase shifter 2401 that produces a second output having a quadrature phase modulation component for the first input light entering the TE branch 2501. When the first output and the second output are combined, TE mode output light with four-stage I/Q modulation of the first input light is generated in the TE output line 2503. In addition, in this embodiment, a second I/Q modulator is configured, basically the same as the first I/Q modulator, with four linear waveguide arms of different phase delays to receive four equally split portions of the second input light into TM x branch 2502 through three power splitters in two stages. Similarly, the in-phase and quadrature components (I and Q) are combined using a 90 ° phase shifter 2402 to generate a TM x mode output light in TM x output line 2504 with four-level I/Q modulation of the second input light. Note that even though the TM mode output light is labeled TM, it is still TE mode light originating from the tunable laser 1000.

Since the output light in both the TE and TM output lines are in the TE mode, a Polarization Beam Rotator Combiner (PBRC) combines them at the output to form a coherent optical signal. Referring to fig. 1, coherent transmitter block 2000 further includes PBRC 2200 to rotate TE mode light in TM x output line 2504, which is combined with TE mode light in TE output line 2503, into TM mode light. Optionally, TE attenuator 2301 and TM attenuator 2302 are two variable optical attenuators inserted into TE output line 2503 and TM output line 2504, respectively, to tune the polarization-dependent power loss in the two branches before PBRC 2200. The output of PBRC 2200 is a fully coherent optical signal with a mixed TE/TM mode in I/Q modulation. The output is then fed to a polarization independent Semiconductor Optical Amplifier (SOA)2100 to increase the optical power of the coherent optical signal transmitted from the coherent transceiver. Optionally, variable optical attenuators 2301 and 2302 in the TE and TM paths may also be used to tune the residual polarization dependent gain in the polarization independent SOA 2100. Alternatively, the use of a polarization independent SOA2100 at the output of the coherent transmitter block 2000 allows a wide range of output power from a coherent optical transceiver regardless of the polarization state of the optical signal. Alternatively, the polarization independent SOA2100 is provided as a flip chip mounted on the silicon photonic substrate 100. Flip-chip mounting of the SOA2100 is similar to flip-chip integration of the driver chip 2600 and the TIA chip 3400 with the silicon photonic substrate 100.

Alternatively, PBRC 2200 is substantially the same type of silicon photonic device that PBSR 3100 operates in the reverse optical path. Specifically, referring to fig. 2A, two TE mode light waves, e.g., TE mode light with I/Q modulation and TM mode light with I/Q modulation, are loaded into two input ports 1901 and 1902 of PBRC, respectively (which are two output ports of PBSR). TE mode light loaded into cross port 1901 remains TE mode at output port 1600 of PBRC (which is the input port of PBSR), while TM x mode light loaded into strip port 1902 (also TE mode light) is rotated 90 degrees to become true TM mode polarized at output port 1600.

Fig. 3 is a simplified diagram of a silicon photonic tunable laser according to an embodiment of the present invention. This diagram is merely an example, which should not unduly limit the scope of the claims. One of ordinary skill in the art would recognize many variations, alternatives, and modifications. As shown, the silicon photonic tunable laser apparatus 10 includes a laser diode flip-chip 400, a tunable filter 200, and integrated couplers 301 and 302, all integrated into a single silicon photonic substrate 100. The silicon photonics substrate 100 includes a patterned region 110 pre-formed with one or more vertical stops 112 and 113, a plurality of alignment features 114, 115 distributed substantially along a first direction z, and a bond pad 111 disposed substantially between the one or more vertical stops 112 and 113. The patterned region 110 is optionally configured as a flat surface region that is one step lower than the remaining flat surface regions 120 substantially separated by the edge 101 along the second direction x. An integrated coupler 301 is disposed near the edge 101 to couple with the tunable filter 200 formed in the silicon photonic substrate 100 so that wavelength tuning can be achieved by the tunable filter 200. The laser diode flip chip 400 is configured to be attached into the patterned region 110 to engage with the bond pads 111 while resting on the vertical stops 112 and 113. At the same time, the step portion along the edge 101 also serves as an edge stopper against the end of the laser diode chip 400. Finally, the laser light that has been tuned by the tunable filter 200 is output from the opposite face of the laser diode chip 400. Referring to fig. 1 and 3, an integrated coupler 302 may be used to couple the laser output into a silicon line waveguide in the same silicon photonic substrate 100 to deliver laser light to either of a receiver block 3000 and a transmitter block 2000.

In particular embodiments, tunable filter 200 is configured as a vernier ring reflector filter. Optionally, tunable filter 200 is a Si wire waveguide 220 fabricated in silicon photonic substrate 100. Optionally, tunable filter 200 is formed in the remaining flat surface region 120 outside of patterned region 110. The Si wire waveguide 220 includes at least two ring resonators 221 and 222. Alternatively, the two ring resonators are made with slightly different radii. Optionally, the first ring 221 is coupled to a reflector ring 223, which reflector ring 223 is also made of a linear part of a Si wire waveguide coupled to the ring-like structure via a 1-to-2 splitter. Optionally, the second ring 222 is coupled to the integrated coupler 300 via a linear line waveguide 210 made of a different material. Optionally, the linear line waveguides 210 are SiN-based waveguides formed in the same silicon photonic substrate 100.

In an embodiment, tunable filter 200 further comprises: a first ring heater (ring1_ HTR)201 having a thin film resistive layer covering the first ring 221; a second ring heater (ring2_ HTR)222 having a resistive film covering the second ring 222; and a phase heater (phase _ HTR)203 covering the reflector ring 223. By varying the voltage supplied to the two ring heaters (201 and 202) to vary the temperature, multiple resonance peak positions in the transmission spectrum can be tuned by each of the two ring resonators (221 and 222). Because the two rings have different radii, there is a shift between the two transmission spectra when they overlap (see fig. 8). When light passes through the reflector ring 223, a reflection spectrum having a strong peak is generated (see fig. 9), and the spectrum can be tuned by changing the temperature by changing the voltage supplied to the phase heater (203). Optionally, each heater is made of a resistive film geometrically covering each ring-shaped wire waveguide and terminated to two bond pads for bonding to an external power supply.

In an embodiment, the laser diode chip 400 includes a gain region. The gain region includes an InP-based active region that is driven to produce laser light. Laser light originally generated from the InP active region is input into the tunable filter 200 via the integrated coupler 301 and the linear line waveguide 210. The light will pass through the at least two ring resonators 222 and 221 and be reflected back to the gain region of the laser diode chip 400 by the reflector 223. As shown in fig. 10, the reflectance spectrum produces a strong lasing peak at the wavelength. The wavelength is tunable by tuning phase heater 203 over a wide band of at least 1560nm to 1530nm as shown in fig. 10. If the integral of the entire optical path of the tunable laser device 10 is equal to N2 pi (N is an integer), light is output as laser light of a fixed wavelength when a round-trip cavity lasing condition is satisfied.

Fig. 4 is a schematic diagram illustrating a perspective view of a laser diode chip flip-chip bonded to a silicon photonics substrate in accordance with an embodiment of the present invention. This diagram is merely an example, which should not unduly limit the scope of the claims. One of ordinary skill in the art would recognize many variations, alternatives, and modifications. Referring to fig. 4, a portion of a substrate 100 is shown to include a patterned region 110 located outside of the remaining planar surface region 120. The patterned region 110 is configured as a flat region that is one step lower than the remaining flat surface region 120. Along this step, the edge stopper 101 is formed to face the first direction z. Optionally, the step is along a second direction x perpendicular to the first direction z. On the patterned region 110, a bonding pad 111 is formed along the first direction z. On both sides of the bonding pad 111, there are two vertical stoppers 112 and 113, which are two thin plates having a certain height. The two extensions 117 of the bonding pad 111 are used for bonding with an external source. Further along these vertical stops, a plurality of alignment features 115 are formed. Optionally, the alignment feature 115 comprises a plurality of fiducials arranged in one or two rows along the first direction z.

In this embodiment, the laser diode chip 400 having the gain region 410 and the metal electrode 411 formed in an elongated shape on the top may be fabricated in advance. The gain region 410 is formed from one edge of the chip to the other. Alternatively, the metal electrode 411 is formed in contact with the P-side layer of the active region made of an InP-based P-N junction quantum well structure. On both sides of metal electrode 411, alignment features 415 are formed on the laser diode die and are configured to match the plurality of fiducial points of alignment features 115 on patterned region 110. Referring to fig. 4, the laser diode chip 400 is a flip chip bonded to the patterned region 110 of the substrate 100. The patterned region 110 and the laser diode chip 400 are each configured such that when the alignment features 415 of the latter engage the plurality of fiducial points 115 of the former, the latter abuts the vertical stops 112 and 113 of the former, with the edges of the latter abutting the edge stops 101 of the former.

Fig. 5 is an exemplary diagram of a wavelength tuning diagram of a silicon photonic tunable laser according to an embodiment of the present invention. This diagram is merely an example, which should not unduly limit the scope of the claims. One of ordinary skill in the art would recognize many variations, alternatives, and modifications. As shown, the graph is plotted as a spectral frequency 2D map as a function of power supplied to the two power supplies of the two ring heaters in the tunable filter described above. The dashed rectangle gives the possible tuning range. Since the two ring resonators are provided with different radii, it effectively produces an extended tunable range of spectral wavelengths when the two transmission spectra are superimposed when they are physically coupled, such as in a vernier ring filter configuration (see fig. 8). Alternatively, the long side of the rectangle provides a relatively coarse wavelength tuning range of 50nm or more (e.g., from about 1520nm to about 1575nm), and the short side of the rectangle provides a relatively fine wavelength tuning range of about 10nm (e.g., from about 1565nm to about 1575 nm).

Fig. 6 is a simplified diagram of a silicon photonic tunable laser apparatus according to another embodiment of the present invention. This diagram is merely an example, which should not unduly limit the scope of the claims. One of ordinary skill in the art would recognize many variations, alternatives, and modifications. As shown, the tunable laser device 40 includes: a first laser diode chip 430 bonded to the first patterned region 410 of the substrate 100; a second laser diode chip 440 bonded to the second patterned region 420 of the substrate 100; a tunable filter 470 coupled to the first gain region 435 of the first laser diode chip 430 via a first integrated coupler 451 and to the second gain region 445 of the second laser diode chip 440 via a second integrated coupler 460; a wavelength locker 480 configured to lock the wavelength of reflected light from the second gain region 445 through the tunable filter 470 and to enable a laser output at the end face 432 of the first gain region 435, wherein the third integrated coupler 452 is operable to couple the laser output to the silicon wire waveguide. Referring to fig. 1 and 6, laser light output from a tunable laser 1000 may be coupled via an integrated coupler 452 to a waveguide in a silicon photonic substrate 100, which silicon photonic substrate 100 is further transported via the waveguide through a power splitter 1001 to both a coherent receiver block 3000 and a coherent transmitter block 2000.

Referring to fig. 3 and 6, each of the first and second laser diode chips 430 and 440 of the tunable laser 40 is configured substantially the same as one laser diode chip 400 having a metal electrode in contact with the P-type layer of the corresponding active region and flipped (flip down) such that the metal electrode is bonded to the bond pads of the first and second patterned regions 410 and 420 in the same substrate 100. Specifically, the first laser diode chip 430 is configured as a cavity having a first end face 431 and a second end face 432 with a gain region 435 joined therebetween as a line waveguide along the active region. When the first laser diode is flip-chip (P-side down) bonded to the first patterned region 410, the first end face 431 abuts an edge stop associated with the first patterned region 410 to align with the first integrated coupler 451. The silicon wire waveguides associated with the first gain region 435 are configured in a curved shape having a non-perpendicular angle with respect to each of the first and second end faces 431, 432 to reduce direct back reflection of light from the respective end face. Optionally, the first end surface 431 includes an anti-reflective coating. Optionally, the second end face 432 is also coated with an anti-reflective coating to facilitate laser output. The first laser diode chip 430 is driven by a driver to produce light as input light into the tunable filter 470 via the first waveguide 491. The second laser diode chip 440 is configured as a cavity with a third end face 441 and a fourth end face 442, with the gain region being joined between them as a silicon wire waveguide along the active region. When a second laser diode chip is flip-chip (P-side down) bonded to the second patterned region 420, the first end face 441 abuts an edge stop associated with the second patterned region 420 to align with the second integrated coupler 460. Optionally, the third end face 441 is coated with an anti-reflection coating and the fourth end face 442 is coated with a highly reflective coating to enhance the reflection of the input light. The reflected light may pass through the second integrated coupler 460 back to the tunable filter 470 via the second waveguide 492, so that the cavity of the second gain region 445 may also serve as a ring reflector for the tunable filter in a substantially upstream standard ring reflector configuration, in addition to providing gain to the reflected light.

In an embodiment, the tunable filter 470 of the tunable laser 40 is a Si wire waveguide fabricated in the substrate 100, in particular in the region 120 outside the first patterned region 410 and the second patterned region 420. Tunable filter 470 includes two ring resonators, a first ring resonator 471 and a second ring resonator 472 coupled to each other. The two ring resonators are coupled to the first waveguide 491 via a 2-to-1 coupler 473 and to the second waveguide 492 via another 2-to-1 coupler 474. Alternatively, the 2-to-1 coupler still has the form of a waveguide with one port at one end and two ports at the opposite end. Alternatively, it is a splitter from one port end to both port ends, or a combiner from both port ends to one port end. Both the first waveguide 491 and the second waveguide 492 are fabricated in the region 120 of the substrate 100 to couple with the first integrated coupler 451 and the second integrated coupler 460, respectively. The first integrated coupler 451 is disposed alongside an edge stop associated with the first patterned region 410. The second integrated coupler 460 is disposed alongside an edge stop associated with the second patterned region 420. Optionally, each of the first waveguide 491 and the second waveguide 492 is made of SiN material embedded in the Si-based substrate 100. Optionally, the line waveguide of tunable filter 470 is made of Si material.

Referring to fig. 4, tunable filter 470 of tunable laser 40 further includes: a first heater (Ring1_ HTR) having a resistive thin film covering the first Ring resonator 471; a second heater (Ring2_ HTR) having a resistive film covering the second Ring resonator 472; and a third heater (Phase _ HTR) having a resistive film covering the Phase shifter portion 475 of the Si line waveguide connected to the second waveguide 492. The heaters are configured to change temperature to cause a change in the transmission spectrum of light passing through the respective ring resonators. The transmission spectrum of each ring resonator has a plurality of resonance peaks (see fig. 6). In an embodiment, the two ring resonators 471 and 472 are set with slightly different radii, and then there is a shift between the two transmission spectra when they overlap (see fig. 6). The first and second heaters are capable of controllably varying the temperature of the respective first and second ring resonators to move the respective resonance peaks to provide an extended tunable range of wavelengths of those resonance peaks. After the input light that passes through tunable filter 470 is reflected back by the cavity of second gain region 445, the reflectivity spectrum will give a stronger central peak (see fig. 9), which can be further tuned by changing the temperature of phase shifter portion 475 using a third heater. In this case, since tunable filter 470 is configured as a vernier ring reflector, second gain region 445 acts as a ring reflector, while phase shifter portion 475 is formed in close proximity to the reflector rather than separate from the reflector, as shown in fig. 10.

Optionally, the tunable filter 470 of the tunable laser 40 includes a fourth heater having a resistive film covering a portion of one branch of the 1-to-2 coupler 473 to finely balance the power of the input light split from the first waveguide 491 into two branches coupled to the two ring resonators 471 and 472, respectively.

In this embodiment, the wavelength locker 480 is configured as a Delay Line Interferometer (DLI) based on a Si waveguide formed in the substrate 100. Optionally, the wavelength locker 480 includes an input port coupled to the first waveguide 491 via a splitter to receive reflected light from the tunable filter 470. Optionally, one end of the input port is a SiN waveguide, also made of SiN material, coupled to the first waveguide 491. The other end of the input port is connected to a 1-to-2 splitter 481 to direct a portion of the light to monitor port PM0 and another portion of the light to the DLI via another 1-to-2 splitter 482. The light then exits the DLI via the 2-to-2 splitter 483 to a first interference output port PM1 and a second interference output port PM 2. In this embodiment, the wavelength locker 480 is pre-calibrated to set the DL1 for locking the wavelength (of the reflected light from the tunable filter) to certain channel wavelengths of the broadband. Alternatively, the channel wavelength provided by tunable laser 40 is an ITU channel in the C-band for DWDM applications. Of course, the disclosure of the tunable laser 40 is applicable to O-band light sources for CWDM applications. Optionally, the tunable laser 40 is integrated in a coherent transceiver, in a coherent receiver block and a coherent transmitter block on substantially the same silicon photonic substrate (see fig. 1). Optionally, each of the monitor port PM0, the first interference output port PM1, and the second interference output port PM2 is terminated with a photodiode for measuring optical power as a function of photocurrent. A differential signal, characterized by the difference in photocurrent between PM1 and PM2, is collected and fed back as an error signal to the drivers of the first and second laser diode chips to adjust the wavelength of the light. Ideally, the error signal should be zero when adjusting or locking the wavelength to the desired ITU channel for pre-calibration of the wavelength locker, i.e. PM 1-PM 2.

In another aspect, the present disclosure also provides a method for tuning the wavelength of a tunable laser device based on silicon photons as described above. Fig. 7 is a flow chart of a method for tuning the wavelength of the laser output of a silicon photonic tunable laser apparatus according to an embodiment of the present invention. As shown, the method comprises the following steps: light having a wavelength near the ITU channel (e.g., in the C-band) is generated in a dual gain configuration including a first active region and a second active region. Referring to fig. 6, in a specific embodiment, a first laser diode chip having a first metal electrode in contact with the P-type layer of the first active region and a second laser diode chip having a second metal electrode in contact with the P-type layer of the second active region are provided. Further, a first laser diode chip having a first metal electrode is flip-bonded to the bond pad in the first patterned region of the substrate to align the first active region with the first integrated coupler, and a second laser diode chip having a second metal electrode is flip-bonded to the bond pad in the second patterned region of the substrate to align the second active region with the second integrated coupler. The first active region and the second active region are connected via a silicon photonic tunable filter to form a combined resonant cavity. Referring to fig. 7, the method includes driving a first laser chip and a second laser diode chip to generate light in a combined resonator cavity. Specifically, the method comprises the following steps: light is input with gain from a first active region of a first laser diode chip driven by its driver. Input light having a gain from the first active region is coupled into the first integrated coupler and into a first waveguide that directs the input light to a silicon-photon based tunable filter. In addition, input light from the first active region enters the tunable filter through the first integrated coupler via the first waveguide, and further enters the second active region via the second waveguide and through the second integrated coupler, and is reflected therefrom with additional gain, thereby achieving dual gain by combining the round-trip paths of the resonant cavities.

Referring to fig. 7, the method further includes reflecting light with additional gain from the second active region of the second laser diode chip. The reflected light from the second active region with additional gain further passes through the second integrated coupler and returns to the tunable filter via the second waveguide.

In addition, the tunable filter is configured to have a first ring resonator ring1, a second ring resonator ring2, and a phase shifter section. The method further comprises the following steps: a first heater associated with the first ring resonator, a second heater associated with the second ring resonator, and a third heater associated with the phase shifter are respectively disposed to set a wavelength near the ITU channel. The first heater, the second heater, and the third heater are respectively configured as a resistive thin film formed in the substrate to at least partially cover the first ring resonator ring1, the second ring resonator ring2, and the phase shifter portion. Each of these heaters is controllable by a voltage applied to the two coupling electrodes from an external power supply. In a specific embodiment, this step includes reading voltages respectively set for the first heater, the second heater, and the third heater from a preset look-up table (LUT). The voltage read from the LUT is substantially related to the corresponding ITU channel. For example, specific voltage values are preset for the wavelength of 1535nm in the C-band. Further, the step includes applying the voltages read from the LUT to the first heater and the second heater, respectively, to set two transmission spectra of the first ring resonator and the second ring resonator, respectively, to obtain a composite spectrum having a strong peak wavelength in the extended tunable range. For example, the extended adjustable range may vary between 1520nm to 1570 nm. In another example, the extended tunable range may vary at least between 1535nm to 1565nm when the gain profile is relatively limited. Further, this step includes applying the voltage read from the LUT to a third heater to set the phase of the reflectance spectrum having a strong peak wavelength in the extended tunable range. The reflection spectrum is set substantially based on the synthesized spectrum.

Referring to fig. 7, the method further includes monitoring the photocurrent at a monitor port, a first interferometric output port, and a second interferometric output port, which are separate from the input port of the wavelength locker (see fig. 6), based on light reflected from the second active region and filtered by the tunable filter. Each of the monitor port, the first interference output port, and the second interference output port is terminated with a photodiode (e.g., PM0, PM1, and PM2, see fig. 6), respectively. Each of these photodiodes produces a photocurrent as a measure of its optical power, which can be monitored in real time. An error signal based on the differential optical power between the first and second interferometric output ports may be used as feedback to tune the optical wavelength to be locked to, for example, a pre-calibrated wavelength of the ITU channel.

Further, the method includes tuning the first and second heaters to coarsely tune the transmission spectrum through each of the first and second ring resonators until the photocurrents at the first and second interferometric output ports are equal. Since the first ring resonator and the second resonator are assigned slightly different radii, there is a shift between the two transmission spectra. By superimposing the two transmission spectra, a composite spectrum can be obtained which comprises at least one strong peak, since both transmission peaks of the two ring resonators fall within the same wavelength. By tuning the first and second heaters, the location of the strong peak in the synthesized spectrum will be shifted over an extended tunable range. When the photocurrents at the first and second interferometric output ports are equal, which means that when the error signal goes to zero, the peak wavelength is substantially tuned to match the pre-calibrated wavelength locked by the wavelength locker. Of course, the wavelength locker 480 may be configured to combine in different ways with the tunable filter 470 configured as a vernier ring reflector to achieve the wavelength locking function. Many different silicon photonics based wavelength locker configurations may be referred to in commonly assigned U.S. patent No. 10056733 to Inphi, inc.

The method further includes tuning the third heater to fine tune the reflection spectrum by maximizing a photocurrent of a monitor port of the wavelength locker representative of a maximum gain from the round-trip cavity lasing conditions associated with both the first active region and the second active region. The phase shifter section of the tunable filter is located on the straight section of the Si wire waveguide outside the two ring resonators. When a third heater located at least partially over the phase shifter portion is tuned to change the temperature of the phase shifter portion, the phase of the reflected light can be tuned according to the entire round trip path between the first active region and the second active region. The laser emission condition is the maximum gain obtained at the phase optimized by the physical arrangement and phase shift part of the optical path between the first active region and the second active region, characterized by the maximum power measured by the photocurrent at the monitor port of the wavelength locker. An enlarged cavity with two active areas will undoubtedly enhance the lasing power of the tunable laser device on a single active area.

Fig. 8 is a schematic diagram of two superimposed transmission spectra of respective two ring resonators having different radii of a tunable filter in a silicon photonic tunable laser apparatus according to an embodiment of the present invention. This diagram is merely an example, which should not unduly limit the scope of the claims. One of ordinary skill in the art would recognize many variations, alternatives, and modifications. As shown, each transmission spectrum of the ring resonator contains a plurality of peaks that are spaced apart depending on the radius of the ring. Since two different radii are provided for ring1 and ring2, which results in two different non-spectral ranges (SFRs), there is a shift between the two transmission spectra. However, two particular peaks from the two transmission spectra, respectively, may fall to a substantially common wavelength, for example, about 1540 nm.

FIG. 9 is an exemplary graph of reflectivity spectra of reflectors coupled to two ring resonators of a tunable filter according to an embodiment of the present invention. This diagram is merely an example, which should not unduly limit the scope of the claims. One of ordinary skill in the art would recognize many variations, alternatives, and modifications. After superimposing the two transmission spectra when the light passing through the two ring resonators is recombined in the single straight portion of the line waveguide and reflected from the second active region, the obtained reflection spectrum is substantially based on a composite spectrum of the two transmission spectra. As shown, the reflectance spectrum is characterized by at least one strong peak at a wavelength of, for example, about 1540 nm.

Figure 10 is a simplified block diagram of a tunable filter including two ring resonators, one reflector plus one phase shifter in a vernier ring reflector configuration in accordance with an embodiment of the present invention. This diagram is merely an example, which should not unduly limit the scope of the claims. One of ordinary skill in the art would recognize many variations, alternatives, and modifications. As shown, the tunable filter includes three parts: two ring resonators and a phase control section. The FSRs of the two ring resonators are slightly different, which can extend the tuning range to the lowest common multiple of the FSRs by a vernier effect. One phase control section is a loop reflector formed by a loop waveguide and a directional coupler. Alternatively, the loop reflector may be replaced by a facet of another laser diode chip. The other phase control section may simply be a waveguide section with an additional heater for directly tuning the phase based on thermo-optical effects. The reflection spectrum is basically a composite spectrum obtained by superimposing two circular spectra. The external laser cavity is arranged between an aspect of the (first laser diode chip) active area and the loop reflector. The lasing operation occurs when the peaks of the transmission spectrum through the rings are identical and the phase is adjusted on the peaks of the rings. Of course, the tunable filter is configured with a variety of variations in terms of the arrangement of the ring resonators and the phase control section, resulting in different synthesized spectra.

Fig. 11 is an exemplary diagram of two composite spectra corresponding to a wavelength tuned from 1555nm to 1535nm by tuning a tunable filter in a vernier ring reflector configuration and a corresponding gain profile from 1530nm to 1570nm, respectively, in accordance with an embodiment of the present invention. This diagram is merely an example, which should not unduly limit the scope of the claims. One of ordinary skill in the art would recognize many variations, alternatives, and modifications. As shown, for different SFRs, the resultant spectrum is characterized by a strong peak due to the superposition of two transmission spectra having a common multi-peak wavelength. The peak position or wavelength value can be tuned by tuning the vernier ring reflector around the optimal center position over an extended tuning range.

Fig. 12 is an exemplary graph of a laser spectrum output by a silicon photon tunable laser apparatus according to an embodiment of the present invention, wherein the laser wavelength is tuned from 1555nm to 1535 nm. This diagram is merely an example, which should not unduly limit the scope of the claims. One of ordinary skill in the art would recognize many variations, alternatives, and modifications. As shown, the laser wavelength is indicated by the peak of the spectrum, which can be tuned over the C-band (or other broadband band) by tuning the vernier ring reflector response. In the example, the laser wavelength is tuned from 1555nm to 1535 nm. A tunable filter based on a vernier ring reflector configuration is used as a wavelength selective filter for the gain profile. The center or optimum position of the gain profile can be initially preset by setting the optimum temperature using the pre-calibrated voltage supplied to the resistive heaters associated with ring1, ring2 and the phase shift section. For example, the pre-calibrated voltages may be stored in a look-up table in memory, which may be read each time the silicon-photon based tunable laser device is initialized. Coarse tuning of the wavelength can be achieved by varying the temperature around ring1 and ring2 to tune the wavelength over an extended tunable range around the location of the optimum gain profile set by the initial configuration of the heaters associated with ring1, ring2 and the phase shifting section. Fine wavelength tuning can be performed by changing the temperature around the phase shifting portion. The lasing region also has a wavelength dependent gain profile that is much wider than the gain profile from the ring.

FIG. 13 is a schematic diagram of three types of SiN based integrated couplers in Si waveguides, according to some embodiments of the invention. This diagram is merely an example, which should not unduly limit the scope of the claims. One of ordinary skill in the art would recognize many variations, alternatives, and modifications. Like FSR, the coupling coefficient of a tunable filter with two ring resonators is an important parameter to achieve a large modal gain difference to obtain a sufficiently high side-mode suppression ratio compared to the other modes. One key factor in determining the coupling coefficient is the alignment of the optical mode confined in the integrated coupler with the input laser beam. On the other hand, misalignment tolerances present with different integrated coupler designs would be an advantage in improving the productivity of tunable laser devices.

Referring to fig. 13, a first type of integrated coupler design is an inverted nanocone structure made of SiN material embedded in a Si waveguide with a sharp tip pointing towards the waveguide end. For this design, a smaller mode diameter is shown, resulting in greater coupling loss in response to relatively small misalignments. A second type of integrated coupler design is a trident structure made of SiN material embedded in a Si waveguide. The SiN trident structure comprises a SiN nanocone, wherein the transverse part of the length of the SiN nanocone is clamped in the middle by two SiN symmetrical nanocones, and the two SiN symmetrical nanocones extend to the waveguide end of the coupler. The large mode diameter of the design is shown, thereby reducing coupling losses due to misalignment. A third type of integrated coupler design is a fork-like structure made of SiN material embedded in a Si waveguide. The forked structure comprises a SiN nanocone sandwiched laterally over its entire length by two SiN linear strips up to the waveguide end. It has a medium-sized mode diameter but coupling losses are minimal, especially for small misalignments between the optical mode and the laser spot.

Fig. 14A is an exemplary graph of the relationship between coupling loss and lateral misalignment of an integrated coupler coupled between a tunable filter and a laser diode chip, according to an embodiment of the invention. This diagram is merely an example, which should not unduly limit the scope of the claims. One of ordinary skill in the art would recognize many variations, alternatives, and modifications. As shown, the SiN trident and SiN fork integrated coupler can replace a SiN reverse nanocone integrated coupler to offset lower coupling loss, and has a considerable tolerance to the misalignment of the transverse axis between the laser beam emitted by the laser diode chip and the mode diameter of the integrated coupler. In this example, the coupling loss from the modes is based on a 2.5 μm laser diode spot size mismatch. Fig. 14B is an exemplary graph of the relationship between coupling loss and vertical misalignment of an integrated coupler coupled between a tunable filter and a laser diode chip, according to an embodiment of the invention. This diagram is merely an example, which should not unduly limit the scope of the claims. One of ordinary skill in the art would recognize many variations, alternatives, and modifications. As shown in the figure, the SiN trident and SiN fork type integrated coupler can replace a SiN reverse nano cone type integrated coupler to offset lower coupling loss, and has a relatively high tolerance on vertical axis misalignment between a laser beam emitted by a laser diode chip and a mode diameter of the integrated coupler. Additionally, the SiN tine integrated coupler provides a more compact design and lower coupling loss (e.g., less than 1dB) than the SiN three-prong integrated coupler. In the example, the length of the forked integrated coupler is only half of the length of the three-prong integrated coupler. In an example, when the misalignment in either the lateral or vertical direction is less than 0.6 μm, the fork-type coupling loss is only half of the trident-type coupling loss.

In an embodiment, the coherent optical transceiver is integrated in a single chip. Fig. 15A shows a perspective view of a coherent optical transceiver chip integrated on a silicon photonics substrate. Fig. 15B shows a side view of a coherent optical transceiver chip. Referring to fig. 15A, the top surface of the silicon photonic substrate 100 is provided as a substrate for integrating all components of the coherent optical transceiver chip 5000. Coherent optical transceiver chip 5000 has a fiber coupler 520 configured to hold first and second optical fibers 511 and 512, respectively, coupled to silicon photonic substrate 100. The coherent optical transceiver chip 5000 comprises a tunable laser device 1000, the tunable laser device 1000 comprising two Laser Diode (LD) chips, a first LD 430 and a second LD 440, both flip-chip mounted on a first area of a silicon photonic substrate 100. Both LD chips 430 and 440 are coupled with a wavelength tunable part embedded in the first region, as shown in fig. 15A. The tunable laser apparatus 1000 is substantially similar to the tunable laser 40 shown in fig. 6. The two laser diode chips 430 and 440 are configured as p-side electrodes with two corresponding gain regions (also referred to as 430 and 440) mounted face down on the silicon photonic substrate 100. The substrate 100 is pre-patterned with a plurality of surface reference points for mounting and aligning the LD chip, vertical stoppers, edge stoppers, and bonding pads. The LD chip 430 and the LD 440 are mounted such that the respective rear end faces of the two gain regions are optically aligned with the wavelength tuning filter 470 and the wavelength locker 480. Meanwhile, the LD chip 430 is mounted such that the front end face of the first gain region outputting laser light is coupled into a waveguide leading to a silicon photonic circuit. Alternatively, wavelength tunable filter 470 and wavelength locker 480 are made directly from a line waveguide in the first region of silicon photonic substrate 100. Alternatively, they are made of silicon and silicon-related materials embedded in the silicon photonics substrate 100. Specifically, the wavelength locker 480 includes a delay line interferometer and a plurality of optical power monitors made of silicon or silicon nitride waveguides. Wavelength tunable filter 470 includes two or more microring resonator waveguides 471 and 472 followed by linear waveguides 491 and 475 coupled to first gain region 430 and second gain region 440, respectively. The radii of the two or more ring resonators are slightly different so that light coupled to the two gain regions is multiply reflected therein at least 90% reflectivity and tuned over an extended wavelength range of the composite spectrum by at least one resistive heater partially covering each of the two or more micro-ring resonator waveguides and a heater covering a portion of the linear waveguide 475 as a phase shifter. Alternatively, power for the resistive heater and the LD driver is provided through electrical connections embedded in the substrate 100 and a plurality of Through Silicon Vias (TSVs) in the substrate 100 to connect with some of the conductive bumps of the grid array (BGA) at the bottom surface of the substrate 100 (as shown in fig. 15B).

In this embodiment, the coherent optical transceiver chip 5000 further includes a transimpedance amplifier (TIA) chip 3400 flip-chip mounted on the second area of the silicon photonic substrate 100. The TIA chips 3400 are electrically coupled to respective electrical connections embedded in the silicon photonics substrate 100 or to a BGA at the bottom surface of the substrate 100 through some TSVs. The silicon photonics substrate 100 may be mounted using a Printed Circuit Board (PCB) to provide the required electrical connections for the TIA chip to operate the optical transceiver 5000. Optionally, the TIA chip 3400 is configured to prepare voltage signals converted from mixed current signals detected from the input coherent optical signal. In addition, the coherent optical transceiver chip 5000 includes a driver chip 2600 flip-chip on the third area of the silicon photonic substrate 100. The driver chip 2600 is electrically coupled to a corresponding electrical connection embedded in the substrate 100 or connected to the BGA at the bottom surface of the substrate 100 through some TSVs, and the electrical connection is completed using a PCB.

Furthermore, the coherent optical transceiver chip 5000 includes silicon photonic circuitry integrated with the tunable laser device 1000, the TIA chip 3400, and the driver chip 2600. The silicon photonics circuit is formed directly in a fourth region of the silicon photonics substrate 100 that is substantially submerged in the substrate 100. Optionally, the silicon photonic circuit comprises a plurality of silicon photonic devices respectively formed in different geometric portions of the fourth region. Functionally, as shown in fig. 1, the silicon photonic circuit mainly includes a receiver block 3000 and a transmitter block 2000. Referring to fig. 1 and 15A, the receiver block 2000 is configured with a waveguide (not explicitly shown) coupled with the first optical fiber 511 to receive the coherent input optical signal, and with another waveguide (not explicitly shown) coupled with the tunable laser apparatus 1000 to receive the first portion of laser light as a local oscillator signal to assist the TIA chip 3400 in detecting the TM mode and TE mode optical signals in the coherent input optical signal. The transmitter block 2000 is configured to drive modulation of the second portion of laser light from the tunable laser device 1000 using the driver chip 2600 to generate a coherent output optical signal that is output to the second optical fiber 512.

Referring to fig. 15A, although details are not explicitly shown, the silicon photonic circuit includes a first power splitter 1001 formed in the substrate 100, the first power splitter 1001 having an input waveguide 1010 coupled to and aligned with the front facet of the first gain region 430 to receive laser light output from the input waveguide. The first power splitter 1001 is configured to split the laser light into two portions, in an X: y-ratio, the first portion is output to the first output waveguide 1011 and the second portion is output to the second output waveguide 1012. The silicon photonics circuit includes a sub-circuit having at least a Polarization Beam Splitter Rotator (PBSR), a second power splitter, and a pair of optical receivers, configured as the receiver block 3000 shown in fig. 1, integrated in one sub-region 3101 of the fourth region of the silicon photonics substrate 100. Functionally, the polarization beam splitter rotator 3100 has an input waveguide coupled directly to the first optical fiber 511 at the edge of the silicon photonics substrate 100 to receive the coherent input optical signal. PBSR 3100 is configured as a shaped silicon waveguide (see fig. 2A) to receive coherent input optical signals and output TE mode optical signals and TM mode optical signals in the coherent input optical signals to two separate optical paths, fed to two 90 ° hybrid optical receivers 3200 and 3300, respectively. The TM-mode optical signal is substantially a TE-mode optical signal rotated by 90 ° from the TM-mode optical signal of the coherent input optical signal. The second power splitter 3001 is essentially a 3dB coupler to split the first portion of laser light from the first output waveguide 1011 of the first power splitter 1001 into two equal halves. Each half of the laser light is used as a local oscillator signal input to a respective one of the two 90 ° hybrid optical receivers 3200 and 3300 to combine with the respective TE and TM mode optical signals to form a first hybrid optical signal and a second hybrid optical signal. Accordingly, the two 90 ° hybrid optical receivers 3200 and 3300 include photodiodes configured to convert the first and second hybrid optical signals into first and second hybrid current signals, respectively.

Referring to fig. 15A, the silicon photonics circuit also includes a Polarization Beam Rotator Combiner (PBRC) and integrated respective two sub-regions 2301 and 2302 of a fourth region of the silicon photonics substrate 100 configured as a pair of optical modulators of the emitter block 2000 shown in fig. 1. In particular, each pair of optical modulators comprises a silicon waveguide based Mach-Zehnder interferometer configured as an in-phase/quadrature-phase modulator having one in-phase branch and one quadrature-phase branch with a 90 ° phase shifter, each branch biased by a voltage provided by the driver chip 2600 to drive modulation of light received from a second portion of laser light from the second output waveguide 1012 of the first power splitter 1001 and through the silicon waveguide of the modulator itself. Each modulator is configured to output a modulated optical signal having I/Q quadrupolar modulation, substantially in TE mode polarization, originating from laser light from the tunable laser device 1000. PBRC 2200 is coupled to the two in-phase/quadrature-phase modulators to receive the two TE mode modulated optical signals, output one TE mode-preserving modulated optical signal and the other rotate-to-TM mode modulated optical signal, and combine the TE mode modulated optical signal and the TM mode modulated optical signal into a coherently modulated optical signal. Referring to fig. 15A, the silicon photonic circuit further includes a polarization independent semiconductor optical amplifier (PI-SOA)2100 as a chip flip-chip near the edge of the silicon photonic substrate 100 to couple at one end to PBRC 2200 and at the opposite end to second optical fiber 512. The PI-SOA2100 is configured to provide a wide range of output powers for a coherently modulated optical signal. Further, the PI-SOA2100 transmits the amplified coherent optical signal as a coherent output optical signal to a second optical fiber that is output to an output port.

Fig. 15B shows a side view of the coherent optical transceiver chip 5000 of fig. 15A. As shown, the coherent optical transceiver 5000 is integrated on a single silicon photonic substrate 100. The silicon photonics substrate 100 is a silicon photonics chip that includes a waveguide made of silicon-related material formed in a silicon-on-insulator substrate. The top surface of the silicon photonic substrate 100 is configured such that multifunctional chips such as the TIA chip 3400, the driver chip 2600, the laser diode chips 430 and 440, and the semiconductor optical amplifier 2100 are mounted at the respective areas. Optionally, each of these chips is flip-chip mounted by conductive bumps 170 face down in combination with pre-formed bumps on the respective areas. Alternatively, a plurality of conductive through-silicon vias may be formed through the silicon photonics substrate 100 and filled with a conductive material for connecting those chips mounted on top thereof to some grid array 160 on the bottom thereof. Optionally, grid array 160 is designed to mount the integrated coherent optical transceiver 5000 on silicon photonic substrate 100 on a printed circuit board in a modular package.

In another aspect, the present disclosure provides a compact package for an integrated coherent optical transceiver formed on a single silicon photonic chip. Fig. 16A is a schematic diagram of an open package of an integrated coherent optical transceiver according to an embodiment of the present invention. Fig. 16B illustrates a closed package of the integrated coherent optical transceiver of fig. 16A, in accordance with embodiments of the present disclosure. This diagram is merely an example, which should not unduly limit the scope of the claims. One of ordinary skill in the art would recognize many variations, alternatives, and modifications. As shown, the enclosed package 6000A is a fully encased coherent optical transceiver. The open package 6000 has the cover member 150 removed. The package 6000 includes an integrated coherent optical transceiver 5000 mounted on a Printed Circuit Board (PCB)600 in a metal housing. In addition to the cover member 150, the metal case is assembled with a pair of side members 140, and the pair of side members 140 are naturally connected with the base member 130 extending the engaging members 141 to the rear end 131 of the case through the engaging members 141 near the front end region of the case. A pair of side members 140 have a pair of clip structures 145 coupled to a cover member 150. The board body of the PCB 600 is supported on the base member 130 with a plurality of conductive pins 610 formed at an end region of the board body generally at the rear end region 131 of the housing. The package includes a first optical connector receiver 501 configured as an input port and a second optical connector receiver 502 configured as an output port for the transceiver 6000. The input port and the output port are both located at the joint member 141 in front of the front end of the board body of the PCB 600.

The integrated coherent optical transceiver on the silicon photonics substrate 100 is basically a coherent optical transceiver chip 5000 as shown in fig. 15A. Details of coherent optical transceiver chip 5000 may be found in the preceding paragraphs. The back end of the first optical connector receiver 501 is coupled to a first optical fiber 511 and the back end of the second optical connector receiver 502 is coupled to a second optical fiber 512, both of which are held by fiber couplers 520 to be respectively coupled and optically aligned with an input waveguide into a silicon photonic circuit built in the silicon photonic substrate 100 and an output waveguide connected to a polarization independent semiconductor optical amplifier (PI-SOA) 2100. Optionally, the front end of the first optical connector receiver 501 is configured to mate with an optical connector connected to an input optical fiber that carries coherent input optical signals having TE and TM hybrid modes from an optical communication system. The front end of the second optical connector receiver 502 is configured to mate with an optical connector connected to an output fiber that outputs a coherent output optical signal having four-level I/Q modulation in TE mode and TM mode polarization. Depending on the application, the integrated coherent transceiver package 6000A may be configured with a compact form factor to accommodate any system design for coherent optical communications.

In an alternative aspect, the present disclosure provides a light engine apparatus including an optical coherent transceiver integrated on a semiconductor substrate member. For example, the optical coherent transceiver is configured as an integrated coherent optical transceiver as shown in fig. 1. For example, the substrate member is provided as one similar to the substrate 100 of fig. 15B. The light engine apparatus includes a substrate member having a surface region. The light engine apparatus also includes an optical input configured to the input fiber optic apparatus and an optical output configured to the output fiber optic apparatus. In addition, the light engine arrangement includes an emission path disposed on the surface area. The transmit path includes a polarization-independent optical amplifier device coupled to the optical output. The transmit path also includes a polarization beam rotator combiner arrangement coupled to the polarization-independent optical amplifier and to the optical output. The transmit path further includes a dual polarization I/Q Mach Zehnder modulator device coupled to the polarization beam rotator combiner device and coupled to the optical output. The transmit path also includes a driver arrangement coupled to the dual-polarization I/Q Mach Zehnder modulator arrangement and configured to drive an electrical signal to the dual-polarization I/Q Mach Zehnder modulator. Furthermore, the emission path includes a tunable laser device including a laser diode chip having a gain region, the chip having a p-side electrode flipped down and mounted on a substrate member. The gain region is coupled with a wavelength tuning section formed in the substrate member to tune a wavelength of laser light output from the gain region to the waveguide in the substrate member. Also, the transmit path includes a first power splitter coupled to the waveguide that splits the laser light into first light and second light. The second light is coupled to a dual polarization I/Q Mach Zehnder modulator device. In addition, the light engine apparatus further includes a receiving path disposed on the surface area. The receive path includes a second power splitter coupled to the first light. The receive path also includes a pair of 90 ° hybrid receivers. Each of a pair of 90 ° hybrid receivers includes a photodetector arrangement and a hybrid mixer arrangement respectively coupled to two outputs of a polarization beam splitter rotator in the substrate member to receive the optical input and to two outputs of a second power splitter to receive the first light from the tunable laser arrangement to assist in detecting Transverse Electric (TE) mode signals and Transverse Magnetic (TM) mode signals in the coherent input signal. Further, the receive path includes a transimpedance amplifier coupled to each 90 ° hybrid receiver and to each photodetector device that converts the combination of the first light and the optical input into an electrical signal for transmission using the transimpedance amplifier device. The light engine apparatus also includes a heterogeneous assembly configured to form a single silicon photonic device using the substrate member, the emission path, and the reception path.

Optionally, the substrate member comprises a silicon substrate. Alternatively, the transimpedance amplifier is made from silicon germanium bipolar technology. Alternatively, the transimpedance amplifier is made of silicon CMOS technology. Optionally, the transimpedance amplifier is made from indium phosphide technology. Alternatively, the transimpedance amplifier is made from a technology that includes gallium arsenide. Optionally, the data center is configured for a social networking platform, an electronic commerce platform, an artificial intelligence platform, or a human tracking platform. Alternatively,

optionally, the light engine apparatus is coupled to the primary substrate member. For example, the main substrate member provided as the circuit board 600 of fig. 16A is configured to mount the light engine device, the digital signal processing device coupled to the light engine device, the power supply coupled to the light engine device and the digital signal processing device, the microcontroller device coupled to the light engine device to provide one or more controls to the light engine device using one or more control signals, the electrical inputs and outputs configured to the light engine device, the digital signal processing device, the power supply, and the microcontroller device; and an electromechanical configuration including the light engine device, the digital signal processing device, the power supply, the microcontroller device, and electrical inputs and outputs configured to the light engine device, the digital signal processing device, the power supply, and the microcontroller device.

Optionally, the light engine apparatus and the primary substrate member are configured as pluggable apparatus. Optionally, the light engine device and the main substrate member together are configured on a system board member of a communication system intended for data transmission and reception. Optionally, the system board components are arranged in a switching system device spatially arranged in the data center. Optionally, the data center is configured for a social networking platform, an electronic commerce platform, an artificial intelligence platform, or a human tracking platform. Optionally, the data center is coupled to a plurality of data centers spatially distributed throughout a geographic area. Alternatively, the data center is owned by a business company or a government entity.

Optionally, the digital signal processing device comprises a host interface to the switching device and a line interface to the light engine device.

Optionally, the master substrate member comprises an electrical interface to the system substrate member, an optical interface to the system substrate member and a mechanical interface to the system substrate member. Optionally, the mechanical interface is thermally configured to the system plate member using an attachment device, using a thermal interface region coupled to the attachment device.

While the above is a complete description of the specific embodiments, various modifications, alternative constructions, and equivalents may be used. Accordingly, the above description and drawings should not be taken as limiting the scope of the invention, which is defined by the appended claims.