阅读说明：本技术 一种布拉格波导光栅调制器 (Bragg waveguide grating modulator ) 是由 马春良 施跃春 陈向飞 于 2020-06-29 设计创作，主要内容包括：本发明公开一种布拉格波导光栅调制器,包含：主波导、谐振腔波导、反对称定向耦合器；所述主波导一端包含前向输入光口、用于接收TE<Sub>0</Sub>模的入射光,另一端包含后向输出光口、用于输出TE<Sub>0</Sub>模的输出光；所述反对称定向耦合器连接所述主波导和谐振腔波导的耦合段,用于实现所述主波导的TE<Sub>0</Sub>模式光与所述谐振腔波导的TE<Sub>1</Sub>模式光的模式转换；所述谐振腔波导上有反对称光栅,用于实现谐振腔波导中TE<Sub>1</Sub>模式光与TE<Sub>0</Sub>模式光的转换。本发明解决现有布拉格光栅调制器反射光对入射端口器件产生不良影响的问题。(The invention discloses a Bragg waveguide grating modulator, comprising: a main waveguide, a resonant cavity waveguide, and an antisymmetric directional coupler; one end of the main waveguide comprises a forward input optical port for receiving TE 0 The other end of the mode includes a backward output port for outputting TE 0 The output light of the mode; the antisymmetric directional coupler is connected with the coupling sections of the main waveguide and the resonant cavity waveguide and is used for realizing TE of the main waveguide 0 TE of mode light and the resonant cavity waveguide 1 Mode conversion of mode light; the waveguide of the resonant cavity is provided with an anti-symmetric grating for realizing the resonant cavityTE in waveguide 1 Mode light and TE 0 Conversion of mode light. The invention solves the problem that the reflected light of the existing Bragg grating modulator has adverse effect on an incident port device.)

1. A bragg waveguide grating modulator comprising: a main waveguide, a resonant cavity waveguide, and an antisymmetric directional coupler;

one end of the main waveguide comprises a forward directionInput optical port for receiving TE₀The other end of the mode includes a backward output port for outputting TE₀The output light of the mode;

the antisymmetric directional coupler is connected with the coupling sections of the main waveguide and the resonant cavity waveguide and is used for realizing TE of the main waveguide₀TE of mode light and the resonant cavity waveguide₁Mode conversion of mode light;

the resonant cavity waveguide is provided with an anti-symmetric grating for realizing TE in the resonant cavity waveguide₁Mode light and TE₀Conversion of mode light.

2. A bragg waveguide grating modulator as claimed in claim 1 wherein said anti-symmetric grating is inscribed on a sidewall of said resonant cavity waveguide and comprises a first anti-symmetric grating, a second anti-symmetric grating;

the incident light enters from the forward input port and outputs a first TE through mode conversion of the antisymmetric directional coupler₁Mode light to the resonant cavity waveguide;

the first TE₁The module light respectively outputs a first forward TE through the first and second antisymmetric gratings₁Mode-optical, first backward TE₀Performing mold polishing;

the first forward TE₁The mode light outputs second backward TE through the second antisymmetric grating₀Mode light, the first backward TE₀The mode light outputs second forward TE through the first anti-symmetric grating₁Performing mold polishing;

the first and second forward direction TE₁Mode light is converted into the TE through the antisymmetric directional coupler mode₀The output light of the mode is output from the backward output light port.

3. A bragg waveguide grating modulator as claimed in claim 1 wherein said resonant cavity waveguide is a ridge waveguide containing a PN junction, doped carriers and metal electrodes disposed on either side, and wherein TE in said main waveguide is provided without application of an electrical signal₀The effective refractive index of the mode light is equal to the TE of the resonant cavity waveguide₁Mode(s)An effective refractive index of light; TE in the resonant cavity waveguide if an electrical signal is applied₀Mode light and TE₁The effective refractive index of the mode light is changed and is not equal to TE in the main waveguide₀The effective refractive index of the mode light.

4. A bragg waveguide grating modulator as claimed in claim 1 wherein the main waveguide is a rectangular waveguide.

5. A bragg waveguide grating modulator as claimed in claim 1 wherein the grating period of the antisymmetric grating is:

wherein Λ is the grating period, λ is the wavelength of the incident light, n_eff0、n_eff1Respectively TE of the resonant cavity waveguide₀Mode light, TE₁The effective refractive index of the mode light.

6. A Bragg waveguide grating modulator as claimed in claim 1, wherein the antisymmetric grating satisfies the Bragg condition β₀+β₁-K₀₁0, wherein, β₀And β₁Respectively TE in the resonant cavity waveguide₀Mode light and TE₁Propagation constant of mode light, K₀₁In the form of a vector of a grating,Λ is the grating period of the Bragg waveguide grating modulator.

7. A bragg waveguide grating modulator as claimed in claim 1 wherein said main waveguide and said cavity waveguide are fabricated on a silica-on-silicon wafer.

8. A bragg waveguide grating modulator as claimed in claim 1 wherein the anti-symmetric grating is fabricated by a single step of photolithography and etching.

9. A bragg waveguide grating modulator as claimed in claim 2 wherein said anti-symmetric grating includes a pi phase shifting structure disposed between said first and second anti-symmetric gratings.

Technical Field

The invention relates to the technical field of communication, in particular to a Bragg waveguide grating modulator.

Background

The modulator is an important device for loading signals in optical fiber communication, the types of structures of the silicon optical modulator are many, and the commonly used structures comprise a Mach-Zehnder modulator, a micro-ring modulator and a Bragg grating modulator. In practical application, the arm length of the Mach-Zehnder modulator is generally larger than 2mm, and the Mach-Zehnder modulator is large in size; the micro-ring modulator is easy to crosstalk among different channels; the intrinsic grating reflected light of the existing Bragg grating modulator can cause adverse effects on other devices of an incident port, particularly the light source of a semiconductor laser is very sensitive to external reflected light, and the existing reflected light can cause adverse effects on other devices of the incident port, so that the Bragg grating modulator loses the advantages of external modulation to a great extent.

Disclosure of Invention

The invention provides a Bragg waveguide grating modulator, which solves the problem that the reflected light of the existing Bragg grating modulator has adverse effect on an incident port device.

In order to solve the problems, the invention is realized as follows:

an embodiment of the present invention provides a bragg waveguide grating modulator, including: a main waveguide, a resonant cavity waveguide, and an antisymmetric directional coupler; one end of the main waveguide comprises a forward input optical port for receiving TE₀The other end of the mode includes a backward output port for outputting TE₀The output light of the mode; the antisymmetric directional coupler is connected with the coupling sections of the main waveguide and the resonant cavity waveguide and is used for realizing TE of the main waveguide₀TE of mode light and the resonant cavity waveguide₁Mode conversion of mode light; the resonant cavity waveguide is provided with an anti-symmetric grating for realizing TE in the resonant cavity waveguide₁Mode light and TE₀Conversion of mode light.

Furthermore, the antisymmetric grating is engraved on the side wall of the resonant cavity waveguide and comprises a first antisymmetric grating and a second antisymmetric grating; the incident light enters from the forward input port and outputs a first TE through mode conversion of the antisymmetric directional coupler₁Mode light to the resonant cavity waveguide; the first TE₁The module light respectively outputs a first forward TE through the first and second antisymmetric gratings₁Mode-optical, first backward TE₀Performing mold polishing; the first forward TE₁The mode light outputs second backward TE through the second antisymmetric grating₀Mode light, the first backward TE₀The mode light outputs second forward TE through the first anti-symmetric grating₁Performing mold polishing; the first and second forward direction TE₁Mode light is converted into the TE through the antisymmetric directional coupler mode₀The output light of the mode is output from the backward output light port.

Further, the resonant cavity waveguide is a ridge waveguide and comprises a PN junction and doped carriers, metal electrodes are arranged on two sides of the ridge waveguide, and if no electric signal is applied, TE in the main waveguide is detected₀The effective refractive index of the mode light is equal to the TE of the resonant cavity waveguide₁The effective refractive index of the mode light; TE in the resonant cavity waveguide if an electrical signal is applied₀Mode light and TE₁The effective refractive index of the mode light is changed and is not equal to TE in the main waveguide₀The effective refractive index of the mode light.

Preferably, the main waveguide is a rectangular waveguide.

Preferably, the grating period of the antisymmetric grating is:

wherein Λ is the grating period, λ is the wavelength of the incident light, n_eff0、n_eff1Respectively TE of the resonant cavity waveguide₀Mode light, TE₁The effective refractive index of the mode light.

Preferably, the antisymmetric grating satisfies the Bragg condition of β₀+β₁-K₀₁0, wherein, β₀And β₁Respectively TE in the resonant cavity waveguide₀Mode light and TE₁Propagation constant of mode light, K₀₁In the form of a vector of a grating,

Λ is the grating period of the Bragg waveguide grating modulator.

Preferably, the main waveguide and the resonant cavity waveguide are both manufactured on a silicon dioxide silicon substrate wafer.

Preferably, the antisymmetric grating is fabricated by one-step lithography and etching.

Preferably, the antisymmetric grating contains a pi phase shift structure and is positioned between the first antisymmetric grating and the second antisymmetric grating.

The beneficial effects of the invention include: in the side-coupled antisymmetric Bragg waveguide grating modulator, the main waveguide TE₀Mode light effective refractive index and cavity waveguide backward TE₀Unequal effective refractive index of mode light, resulting in backward TE₀The mode cannot be coupled back to the main waveguide by an anti-symmetric directional coupler (ADC), reducing reflected light; in addition, the invention enables light to be emitted from two sides of the resonant cavity waveguide by increasing the ports, thereby avoiding the situation that the light is reflected from the input port of the main waveguide.

Drawings

The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and together with the description serve to explain the invention and not to limit the invention. In the drawings:

FIG. 1 is an embodiment of a Bragg waveguide grating modulator;

figure 2 is an embodiment of a resonant cavity waveguide.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, the technical solutions of the present invention will be clearly and completely described below with reference to the specific embodiments of the present invention and the accompanying drawings. It is to be understood that the described embodiments are merely exemplary of the invention, and not restrictive of the full scope of the invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

With the advent of the information age, the demand for high-performance data transmission is increasing. In particular, the requirements of people are not limited to the traditional conversation services, but are more focused on the communication at the level of voice, image and the like. Various new services are also emerging, such as multimedia services like video conferencing, video calls, etc. Optical fiber communication has been widely used and studied because it exhibits advantages in terms of transmission capacity, transmission speed, and the like. As an important device for loading signals in optical fiber communication, a modulator has become one of the main research fields.

Silicon has many advantages over other materials: first, the band gap of silicon is 1.12 eV. Therefore, it is transparent in both the O-band and the C-band. Second, the refractive index of silicon is 3.45, while the refractive index of silicon dioxide is 1.45. The silicon and the silicon dioxide have large refractive index difference, and the silicon optical device has large limiting effect on light, so that the size of the device can be smaller. And then, the silicon optical device can be perfectly compatible with the CMOS process, and the cost is lower. Finally, the silicon optical device has better mechanical property and can work in a higher temperature environment. Therefore, silicon optical modulators have shown great potential in the field of optical communications. Nowadays, there are many kinds of structures of silicon optical modulators, and the more commonly used structures include mach-zehnder modulators, micro-ring modulators, bragg grating modulators, and the like.

Currently, the mach-zehnder modulator has the greatest advantage that the operating bandwidth is the full bandwidth, and thus it is widely used. However, the mach-zehnder modulator is large in size. Although the dimensions can be made 0.5mm or less in arm length, the arm length is typically greater than 2mm in practical applications in order to ensure the performance of the modulator. In contrast, micro-ring modulators and bragg grating modulators are resonance-based and therefore may be relatively small in size.

The size of the micro-ring modulator is smaller than that of the mach-zehnder modulator. However, the resonance peaks of the micro-ring modulator are periodic, and when the micro-ring modulators are cascaded, crosstalk between different channels is easy. To avoid channel crosstalk, the diameter of the micro-ring modulator must be small, even less than 10 μm.

The bragg grating modulator is smaller in size than the mach-zehnder modulator. Meanwhile, the Bragg grating modulator is single-mode resonant, so that the Bragg grating modulator only has one resonant peak near the working wavelength, and crosstalk between channels is not easy to occur. However, the grating of a bragg grating modulator inherently reflects light, which can adversely affect the rest of the devices at the input port. In particular, semiconductor lasers are very sensitive to ambient reflected light. This defect is similar to that of the inner modulation. The bragg grating modulator loses the advantage of the outer modulation to a large extent.

Compared with other mainstream silicon optical modulators such as Mach-Zehnder modulators and micro-ring modulators, the Bragg grating modulator has the advantages of small size, single-mode resonance and the like, and crosstalk between different channels is not easy to occur. However, bragg grating modulators also have deficiencies. The reflected light that it presents can have an adverse effect on the rest of the device at the input port. If the isolator or the like is adopted to solve the problem, the cost of the communication system is greatly increased, and the complexity of the structure is increased.

The innovation points of the invention are as follows: first, the present invention adjusts the effective refractive index of the TE0 mode in the main waveguide to be equal to the effective refractive index of the TE1 mode in the cavity waveguide, so that the TE0 mode in the main waveguide can be coupled to the cavity waveguide through the ADC, and the forward TE1 mode of the cavity waveguide can also be coupled back to the main waveguide, but the backward TE mode of the cavity waveguide₀The mode can not be coupled back to the main waveguide due to the difference of the effective refractive index, so that the effect of reducing the reflected light is achieved; second, when the present invention applies an electrical signal, the electrical signal changes the resonator cavity waveguide TE₀And TE₁The effective refractive index of the mode enables incident light to be directly output from an output light port of the main waveguide, and reflected light is avoided; thirdly, the invention comprises two ports besides the two ports of the main waveguide, and the resonant cavity waveguide also comprises two ports, so that light can be emitted from two sides of the resonant cavity waveguide, and the condition that the light is reflected from the input port of the main waveguide is avoided.

The technical solutions provided by the embodiments of the present invention are described in detail below with reference to the accompanying drawings.

Fig. 1 shows an embodiment of a bragg waveguide grating modulator, which can effectively reduce reflected light of an output optical port, and as an embodiment of the present invention, the bragg waveguide grating modulator includes: the waveguide structure comprises a main waveguide 1, a resonant cavity waveguide 2 and an anti-symmetric directional coupler 3, wherein an anti-symmetric grating 21 is arranged on the resonant cavity waveguide.

One end of the main waveguide comprises a forward input optical port for receiving TE₀The other end of the mode includes a backward output port for outputting TE₀The output light of the mode; the antisymmetric directional coupler is connected with the coupling sections of the main waveguide and the resonant cavity waveguide and is used for realizing TE of the main waveguide₀TE of mode light and the resonant cavity waveguide₁Mode conversion of mode light; the resonant cavity waveguide is provided with an anti-symmetric grating for realizing TE in the resonant cavity waveguide₁Mode light and TE₀Conversion of mode light.

In the embodiment of the present invention, the port 1 of the main waveguide is the forward input optical port, the port 2 is the backward output optical port, the port 3 of the resonant cavity waveguide and the forward input optical port are located on the same side of the bragg waveguide grating modulator, and the port 4 of the resonant cavity waveguide and the backward output optical port are located on the same side of the bragg waveguide grating modulator.

The invention aims to use an edge-coupled antisymmetric Bragg waveguide grating modulator, namely the Bragg waveguide grating modulator in the application of the invention, to reduce the inherent reflected light of the traditional Bragg grating modulator and relieve the adverse effect of the reflected light on other devices of an incident port. The side-coupled antisymmetric Bragg waveguide grating modulator is technically based on the following steps: TE in resonant cavity waveguide₀And TE₁Mode can resonate in the antisymmetric grating (ASBWG), and TE₁Effective refractive index of mode less than TE₀The effective refractive index of the mode. Therefore, TE in the main waveguide can be adjusted₀Effective refractive index of the mode is made equal to TE of the resonant cavity waveguide₁The mode effective index. At this time, the main waveguide TE₀Mode energy is coupled to the resonant cavity waveguide through the ADC, forward TE of the resonant cavity waveguide₁Modes can also couple back to the main waveguide, but backward to the TE of the cavity waveguide₀Mode cannot be coupled back to the main waveguide due to the difference in effective refractive index, thereby achieving reductionThe effect of reflecting light.

Note that the antisymmetric grating is an antisymmetric bragg grating.

Further, the antisymmetric grating is engraved on the side wall of the resonant cavity waveguide, and comprises a first antisymmetric grating 22 and a second antisymmetric grating 23.

The incident light enters from the forward input port and outputs a first TE through mode conversion of the antisymmetric directional coupler₁Mode light to the resonant cavity waveguide; the first TE₁The module light respectively outputs a first forward TE through the first and second antisymmetric gratings₁Mode-optical, first backward TE₀Performing mold polishing; the first forward TE₁The mode light outputs second backward TE through the second antisymmetric grating₀Mode light, the first backward TE₀The mode light outputs second forward TE through the first anti-symmetric grating₁Performing mold polishing; the first and second forward direction TE₁Mode light is converted into the TE through the antisymmetric directional coupler mode₀The output light of the mode is output from the backward output light port.

In the embodiment of the present invention, the grating period of the antisymmetric grating is:

wherein Λ is the grating period, λ is the wavelength of the incident light, neff₀、neff₁Respectively TE of the resonant cavity waveguide₀Mode light, TE₁The effective refractive index of the mode light.

In the embodiment of the invention, the antisymmetric grating further comprises a pi phase shift structure 24 positioned between the first and second antisymmetric gratings.

The phase shift of the antisymmetric Bragg grating is realized by adopting any one of the following modes: and a pi phase shift structure is inserted in the middle of the antisymmetric Bragg grating or a planar waveguide moire grating is adopted, namely two lines of waveguide gratings with small grating period difference are adopted.

The antisymmetric grating provides a grating vectorQuantity K₀₁And phase matching between different modes is realized, so that mode conversion is realized. The antisymmetric grating satisfies the Bragg condition:

β₀+β₁-K₀₁＝0 (2)

wherein, β₀And β₁Respectively TE in the resonant cavity waveguide₀Mode light and TE₁Propagation constant of mode light, K₀₁In the form of a vector of a grating,

Λ is the grating period of the Bragg waveguide grating modulator.

Further, TE in the antisymmetric grating₀Mode light and TE₁The coupling coefficient of the mode light is:

wherein, κ₀₁ω is the angular velocity of the incident and reflected light,₀to dielectric constant, Ψ (x)₀Transverse electric field distribution function, Ψ (x), which is a 0-order mode₁Δ (x) is the transverse permittivity distribution as a function of the transverse electric field distribution for the 1 st order mode.

In the embodiment of the present invention, further, the resonant cavity waveguide is a ridge waveguide, which includes a PN junction, doped carriers and metal electrodes disposed on two sides, and if no electrical signal is applied, TE in the main waveguide₀The effective refractive index of the mode light is equal to the TE of the resonant cavity waveguide₁The effective refractive index of the mode light; TE in the resonant cavity waveguide if an electrical signal is applied₀Mode light and TE₁Effective refractive index of mode lightIs not equal to TE in the main waveguide₀The effective refractive index of the mode light.

The main waveguide is a rectangular waveguide without PN junction doping, metal electrodes are not arranged on two sides of the main waveguide, no electric signal is applied, and the effective refractive index of TE0 mode light in the main waveguide is not changed.

In this embodiment, when no electrical signal is applied, the incident light enters the primary waveguide through the port 1 and becomes TE₀A mode optically coupled to the resonant cavity waveguide through the antisymmetric directional coupler and becoming a first forward TE₁Mode light, passing through a second antisymmetric grating, first forward TE₁The mode light is reflected as a first backward TE₀And (4) performing mode light. Due to TE in the waveguide of the resonant cavity₀The effective refractive index of the mode light is not equal to the main waveguide TE₀Effective refractive index of mode, so first backward TE₀Mode light cannot be coupled back into the main waveguide, thus reducing reflected light.

At this time, the first backward TE₀The mode light passes through the first antisymmetric grating and is reflected again as a second forward TE₁And (4) performing mode light. Due to resonant cavity waveguide TE₁The effective refractive index of the mode light is equal to the main waveguide TE₀Effective refractive index of mode light, so first forward TE₁Modulo light and second forward TE₁The mode light can be coupled back to the main waveguide and become TE of the main waveguide₀And a mode generating emergent light.

Further, when an electric signal is applied, according to a plasma dispersion effect, a refractive index of a material of the resonant cavity waveguide changes, and TE of the resonant cavity waveguide changes₀And TE₁The effective refractive index of the mode light decreases accordingly. At this time, the main waveguide TE₀The effective refractive index of the mode light is not equal to the TE of the resonant cavity waveguide₁Effective refractive index of mode light, so TE of the main waveguide₀The mode light cannot be coupled to the resonator waveguide and exits directly from port 2 of the main waveguide.

In the present application, the TE of the main waveguide₀The mode light is all TE including the incident light and the output light₀Mode light, TE of said resonant cavity waveguide₀Mode light including the first forward TE₀Modulo light and second forward TE₀All TE of mode light₀Mode light, TE of said resonant cavity waveguide₁The mode light comprises the first backward TE₁Modulo light and second backward TE₁All TE of mode light₁Mode light.

In the embodiment of the invention, the main waveguide and the resonant cavity waveguide are both manufactured on a silicon dioxide silicon substrate wafer.

In an embodiment of the invention, the antisymmetric grating is manufactured by one-step lithography and etching.

For example, the manufacturing method of the side wall antisymmetric grating sum of the resonant cavity wave band is as follows:

the antisymmetric grating structure is fabricated by a one-step lithography and etching process that is compatible with conventional Complementary Metal Oxide Semiconductor (CMOS) processes. The purpose of photoetching is to transfer the pattern of a mask plate to photoresist on the surface of a silicon wafer. The step can print the image of the mask plate by deep ultraviolet exposure, firstly, the silicon wafer is pretreated, coated with glue, spun and dried, and then the coated silicon wafer is sent into a photoetching machine for exposure. After completion, the wafer is developed, and then the wafer is cleaned and dried.

The purpose of etching is to transfer the pattern on the photoresist on the surface of the silicon wafer to the silicon wafer. This step may be performed by dry etching with Inductively Coupled Plasma (ICP) or wet etching based on chemical reactions. And after the etching is finished, removing the photoresist on the surface of the silicon wafer by using ionized oxygen of a photoresist remover. Alternatively, the lithography may be performed by an electron beam exposure technique, in which a uniform layer of electron beam resist, typically PMMA (polymethyl methacrylate), is first applied to a silicon wafer, and then an electron beam is scanned over the resist using the electron beam exposure technique to form the desired waveguide pattern on the resist by varying the exposure of the electron beam.

As another example, the injection and contact process of the electrical part in the bragg waveguide grating modulator is as follows:

(1) after the etching is completed, the bragg waveguide grating modulator needs to be doped.

Before doping, a layer of silicon dioxide grows on the surface of the wafer, and then the wafer is subjected to photoetching again. And opening a bottom anti-reflection coating (BARC) in the window after photoetching through an etching process after photoetching. And then, carrying out ion implantation on the wafer, removing the photoresist and a bottom anti-reflection coating (BARC) which are used as an implantation mask by a dry photoresist removing method after the implantation is finished, cleaning the wafer by using a hydrofluoric acid solution, a hydrogen peroxide and concentrated sulfuric acid mixed solution and an ammonia water and hydrogen peroxide mixed solution, and then repeating the photoresist removing and cleaning processes after the implantation to finish the doping of PN junction impurities in the ridge waveguide. Then the ridge waveguide flat plate region is doped by injecting the ridge waveguide flat plate region to form an electrical connection structure of a PN junction. In order to form ohmic contact between silicon and metal, a larger dose of dopant ions is implanted into the silicon. And after ion implantation is finished, rapid thermal annealing treatment is carried out to activate implanted impurity ions and repair lattice damage caused by implantation. Here, in order to make the PN junction closer to the abrupt junction, the annealing time is not too long, and 5s may be selected.

(2) Growing silicon dioxide on the surface of the wafer, and flattening the silicon dioxide on the surface of the wafer by a Chemical Mechanical Polishing (CMP) method. The process flow is changed from the front-stage process to the back-stage process. Etching a contact hole of a device on a silicon dioxide layer by using a silicon dioxide etching process, wherein the step is to perform photoetching on a wafer, opening a bottom anti-reflection coating (BARC) coated during photoetching, performing etching by using the silicon dioxide etching process, then performing dry photoresist removal, and finally cleaning to remove residual polymer and photoresist on the surface of the wafer. In order to obtain a better contact resistance, it is usually necessary to metallize the silicon at the contact holes and to form a metal silicide at the contact portions where it is desired to make. And after the etching of the contact hole is finished, cleaning the contact hole by using hydrofluoric acid to remove residual silicon oxide, performing metal deposition after spin-drying, and then performing annealing treatment. And after the treatment is finished, cleaning the wafer, and then annealing the wafer to form the metal silicide with a lower resistance value. After the metal silicide is formed, Ti and TiN are deposited on the surface of the wafer and used as a barrier layer of a contact process. And then growing metal on the wafer through Chemical Vapor Deposition (CVD), filling the silicon oxide contact hole, and removing the redundant metal outside the contact hole through Chemical Mechanical Polishing (CMP). And after the contact hole process is finished, depositing Ti and TiN on the surface of the wafer to be used as a metal barrier layer, then depositing a layer of aluminum alloy, and removing metal on the surface of the wafer through photoetching and etching to only leave the metal connecting wire part of the device. And then depositing silicon dioxide on the surface of the wafer to be used as a cladding, and removing an oxide layer covered on the metal of the part where the device is connected with the outside by photoetching and etching. And finally, annealing the wafer, repairing the metal connecting wire and reducing the resistance of the metal connecting wire.

The embodiment of the invention provides a Bragg waveguide grating modulator, which is a silicon optical modulator based on an antisymmetric Bragg waveguide grating, reduces reflected light on the basis of keeping the advantages of the conventional Bragg grating modulator, and relieves the adverse effect of the reflected light on other devices of an incident port.

Fig. 2 shows an embodiment of a resonant cavity waveguide, which can be used for the resonant cavity waveguide of the bragg waveguide grating modulator of the present invention, in the embodiment of the present invention, metal electrodes 25 are disposed on two sides of the resonant cavity waveguide 2, and are fabricated on a silicon dioxide-based wafer 4.

In the embodiment of the invention, the resonant cavity waveguide is a ridge waveguide and comprises a PN junction and doped carriers, metal electrodes are arranged on two sides of the ridge waveguide, and if no electric signal is applied, TE in the main waveguide is arranged₀The effective refractive index of the mode light is equal to the TE of the resonant cavity waveguide₁The effective refractive index of the mode light; TE in the resonant cavity waveguide if an electrical signal is applied₀Mode light and TE₁The effective refractive index of the mode light is changed and is not equal to TE in the main waveguide₀The effective refractive index of the mode light.

Fig. 2 is a cross section of the resonant cavity waveguide, and in the embodiment of the present invention, the main waveguide of the bragg waveguide grating modulator is a rectangular waveguide, and is not doped with a PN junction, and metal electrodes are not disposed on two sides of the main waveguide, and no electrical signal is applied. The Bragg waveguide grating modulator resonant cavity waveguide is a ridge waveguide, comprises a PN junction, is doped with carriers, and is provided with metal electrodes at two sides.

When an electric signal is applied to the metal electrode, the distribution of current carriers in the resonant cavity waveguide, the width of a PN junction depletion layer and the like are changed. TE in a resonant cavity waveguide based on the effect of plasma dispersion₁Mode light and TE₀The effective refractive index of the mode light changes and, ultimately, the TE of the main waveguide₀Mode light cannot be coupled to the resonator waveguide through an anti-symmetric directional coupler (ADC), and the output optical power of the main waveguide reaches a maximum.

TE of the main waveguide when no electric signal is applied to the metal electrode₀The mode light energy is coupled to the resonant cavity waveguide through an Antisymmetric Directional Coupler (ADC) and resonates in an antisymmetric grating. The emergent light power of the output light port reaches the minimum value, at the moment, light can be emitted from two sides of the resonant cavity waveguide, light is prevented from being emitted from the main wave guide-in emission port, and reflected light is reduced.

It is to be noted that the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising an … …" does not exclude the presence of other like elements in a process, method, article, or apparatus that comprises the element.

The above description is only an example of the present invention, and is not intended to limit the present invention. Various modifications and alterations to this invention will become apparent to those skilled in the art. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention should be included in the scope of the claims of the present invention.