阅读说明：本技术 一种周期性极化型铌酸锂薄膜光波导差频放大器 (Periodically polarized lithium niobate thin film optical waveguide difference frequency amplifier ) 是由 胡哲峰 程书停 陈开鑫 于 2019-12-10 设计创作，主要内容包括：本发明公开一种周期性极化型铌酸锂薄膜光波导差频放大器,应用于集成光学、光通信和微波光子领域,针对现有的光波导放大器存在结构尺寸大、不利于集成、功耗高、制作困难的问题,本发明利用新型的铌酸锂薄膜材料上的非线性差频效应进行光放大,具有结构尺寸小、便于集成到不同基底的器件上、非线性效率高、功耗低、容易制作的优点,可以用作单片集成的光放大器或与其它器件一起形成集成化的系统。(The invention discloses a periodically polarized lithium niobate thin film optical waveguide difference frequency amplifier, which is applied to the fields of integrated optics, optical communication and microwave photon, and aims at solving the problems of large structure size, unfavorable integration, high power consumption and difficult manufacture of the existing optical waveguide amplifier.)

1. A periodic polarization type lithium niobate thin film optical waveguide difference frequency amplifier is characterized in that a core layer, a lower cladding layer and a substrate are sequentially arranged from top to bottom, wherein the core layer is a periodic polarization type lithium niobate thin film; and meanwhile, the pump light and the signal light injected into the periodically polarized lithium niobate thin film generate idle light in the periodically polarized lithium niobate thin film based on an optical second-order nonlinear difference frequency effect, the energy of the pump light is transferred to the signal light and the idle light, and then the signal light after energy amplification is output.

2. The periodically poled lithium niobate thin film optical waveguide difference frequency amplifier according to claim 1, wherein the period of the periodically poled lithium niobate thin film satisfies the following condition:

wherein k is_pRepresenting the wave number, k, of the pump light_sRepresenting wave number, k, of signal light_iRepresents the wave number of idle light, and Λ is the polarization reversal period of the periodically polarized lithium niobate thin film.

3. The periodically poled lithium niobate thin film optical waveguide difference frequency amplifier of claim 2, wherein the amplifier output further comprises a filter for filtering out pump light and idle light.

4. The periodically poled lithium niobate thin film optical waveguide difference frequency amplifier according to claim 2, wherein the periodically poled lithium niobate thin film is in the form of a stripe waveguide or a ridge waveguide.

5. The periodically poled lithium niobate thin film optical waveguide difference frequency amplifier according to claim 2, wherein the lower cladding layer is a silicon dioxide or benzocyclobutene thin film.

6. The periodically poled lithium niobate thin film optical waveguide difference frequency amplifier according to claim 2, wherein the substrate is lithium niobate or silicon.

Technical Field

The invention belongs to the field of integrated optics, optical communication and microwave photons, and particularly relates to an optical waveguide amplifier.

Background

With the continuous development and improvement of optical communication technology, the increase of communication network bandwidth and the diversification of internet and internet of things services bring about the fact that network topology and communication equipment become more complex and the power consumption increases therewith. Therefore, the integrated communication equipment with low power consumption has more important application value in future communication networks. In addition, in a microwave photonic system, an optical amplifier is often required to directly amplify signals in an optical domain, and at this time, devices with integration and low power consumption are further required to meet the strict requirements of vehicle-mounted, airborne and satellite-mounted applications on size, weight and energy consumption. In the rare earth doped or nonlinear optical fiber amplifier widely used at present, because longer optical fiber is used as an amplification medium, the problems of large size, difficult integration and high power consumption are caused, and the rare earth doped or nonlinear optical fiber amplifier is difficult to be applied to an optical communication system and a microwave optical subsystem with more complex functions in the future.

The optical waveguide material is used for manufacturing the optoelectronic device, so that the size of the device can be effectively reduced, and the energy consumption can be reduced, thereby being an important direction for applying the optoelectronic device in the future. The lithium niobate crystal has good electro-optic, acousto-optic and second-order nonlinear coefficients, stable physical and chemical properties, low production cost and easy generation of large-size single crystals, thereby becoming an ideal material for manufacturing optoelectronic devices. The lithium niobate crystal is made into the optical waveguide, so that the optical field can be better limited, the nonlinear effect is more efficient, and the optical waveguide can be better coupled with an optical fiber. In the lithium niobate optical waveguide, the optical second-order nonlinear effect can be used for amplifying an input signal optical field, but phase mismatch is easy to occur in signals and pumping in the nonlinear process, so that the efficiency of nonlinear action is influenced, and phase matching is generally required. Researches show that the second-order polarizability of the lithium niobate crystal is periodically inverted to effectively match the phases of two optical fields and generate a stable nonlinear effect, and the technology is called as a quasi-phase matching technology.

Currently, there are many reports of optical amplification based on the traditional bulk material lithium niobate waveguides. However, the optical waveguide made of lithium niobate, which is a bulk material used in such devices, has a large size, is difficult to integrate, and has insufficient limitation on the energy of the optical field, so that the conversion efficiency is low, and light with large power is generally required to be input as a pump, so that the power consumption is high. The lithium niobate single crystal thin film material newly appeared in recent years reserves the excellent electro-optical and optical characteristics of the lithium niobate material, and because the lithium niobate single crystal thin film material is manufactured on a silicon or benzocyclobutene isolation substrate, the corresponding optical waveguide can be conveniently manufactured into a strip waveguide or a ridge waveguide through a Complementary Metal Oxide Semiconductor (CMOS) compatible etching process. At present, most of researches on the second-order nonlinear optical effect on the lithium niobate thin film are focused on the generation of the nonlinear effect, and the researches on the construction of an integrated functional device or system by using the nonlinear effect are not reported yet.

Disclosure of Invention

In order to solve the technical problem, the invention provides a periodically polarized lithium niobate thin film optical waveguide difference frequency amplifier, which utilizes the nonlinear difference frequency effect of a novel lithium niobate thin film material to amplify light.

The technical scheme adopted by the invention is as follows: a periodic polarization type lithium niobate thin film optical waveguide difference frequency amplifier comprises a core layer, a lower cladding layer and a substrate from top to bottom in sequence, wherein the core layer is a periodic polarization type lithium niobate thin film; and meanwhile, the pump light and the signal light injected into the periodically polarized lithium niobate thin film generate idle light in the periodically polarized lithium niobate thin film based on an optical second-order nonlinear difference frequency effect, the energy of the pump light is transferred to the signal light and the idle light, and then the signal light after energy amplification is output.

Further, the period of the periodically poled lithium niobate thin film satisfies the following condition:

wherein k is_pRepresenting the wave number, k, of the pump light_sRepresenting wave number, k, of signal light_iRepresents the wave number of idle light, and Λ is the polarization reversal period of the periodically polarized lithium niobate thin film.

Further, the output end of the amplifier also comprises a filter for filtering out the pumping light and the idle light.

Further, the periodically poled lithium niobate thin film is in the form of a stripe waveguide or a ridge waveguide.

Further, the lower cladding layer is a silicon dioxide or benzocyclobutene film.

Further, the substrate is lithium niobate or silicon.

The invention has the beneficial effects that: the invention uses the periodic polarization type lithium niobate thin film waveguide to realize the amplification of optical signals, and the waveguide structure is more miniaturized and convenient for integration. The waveguide can be also manufactured on substrates made of different materials, and is beneficial to heterogeneous integration of devices made of different materials, so that the integration of the whole system is realized, and the waveguide is applied to the fields of optical communication, all-optical signal processing, microwave photon and the like; has the following advantages:

1. the structure has small size, is convenient to integrate and is easy to manufacture;

2. the nonlinear efficiency is high;

3. the amplifier of the invention has lower total power consumption;

4. the method can be manufactured on substrates made of different materials, and facilitates heterogeneous integration of devices with different functions.

Drawings

FIG. 1 is a schematic diagram of the second-order optical nonlinear difference frequency effect employed in the present invention.

Fig. 2 is a schematic structural diagram of a strip waveguide provided in an embodiment of the present invention;

fig. 2(a) is a schematic cross-sectional view of a waveguide, and fig. 2(b) is a structural view of the waveguide.

Fig. 3 is a schematic structural diagram of a ridge waveguide according to an embodiment of the present invention;

fig. 3(a) is a schematic cross-sectional view of a waveguide, and fig. 3(b) is a structural view of the waveguide.

Fig. 4 is an input signal optical pulse waveform of a working process simulation provided by an embodiment of the present invention.

Fig. 5 is an output signal optical pulse waveform of a working process simulation provided by an embodiment of the present invention.

Detailed Description

In order to facilitate the understanding of the technical contents of the present invention by those skilled in the art, the present invention will be further explained with reference to the accompanying drawings.

As shown in fig. 1, the wavelengths are respectively λ_pAnd λ_sThe pump light and the signal light are simultaneously injected into the manufactured periodically polarized lithium niobate thin film waveguide. Due to the action of the optical second-order nonlinear difference frequency effect in the medium, two optical fields generate the wavelength lambda when being transmitted in the waveguide_iI.e. idle light is generated. At this time, the energy of the pump light is gradually transferred to the signal light and the idle light, and the output signal light energy is amplified.

The invention adopts the periodically polarized lithium niobate thin film waveguide to realize the amplification of the optical signal, the mode field area of the lithium niobate thin film waveguide is smaller than that of the existing lithium niobate block waveguide, and the total pumping power does not need to be as high as that of the existing lithium niobate block waveguide, namely the total power consumption of the amplifier is lower.

From a quantum-optical perspective, the difference frequency process can be described phenomenologically as: during the action of the pump light, the signal light and the nonlinear medium, annihilation of a pump photon is accompanied by the generation of a signal photon and an idle photon. In this case, the frequencies ω of the pump light, the signal light, and the idle light are set according to the law of conservation of energy_p、ω_sAnd ω_iThe following relation is required

ω_p＝ω_s+ω_i(1)

Because the transmission rates of the three optical fields in the medium are different, phase mismatch is generated in a nonlinear process in an unprocessed lithium niobate waveguide, so that the efficiency of nonlinear action is influenced, and measures are generally required to be taken for phase matching. The invention adopts the quasi-phase matching technology, and ensures the phase matching in the nonlinear process by periodically reversing the nonlinear polarizability of the lithium niobate thin film waveguide, namely meeting the requirement

Wherein k is_p、k_sAnd k_iAre pumps respectivelyWave numbers of the light, the signal light, and the idle light, Λ is a polarization inversion period. After the quasi-phase matching condition is satisfied, the energy of the pump light will be gradually transferred to the signal light and the idle light, and thus the output signal light energy will be amplified. If only signal light output is required at the output, it can be filtered out using a filter; if the residual pump light and idle light at the output end have no influence on the following application, special filtering processing can be omitted.

The structure of the periodically poled lithium niobate thin film optical waveguide employed in the present invention is shown in fig. 2. The waveguide consists of a core layer and an isolation substrate layer, namely a lower cladding and a substrate, wherein the core layer is made of a periodically polarized lithium niobate film, and the lower cladding is made of silicon dioxide or benzocyclobutene film. The structure can be conveniently manufactured on substrates of different materials, such as lithium niobate, silicon and the like, so that the structure can be conveniently integrated or mixed and integrated with other photonic devices to form a system.

The waveguide core layer shown in fig. 2 is a slab waveguide structure, but a ridge waveguide or another waveguide may be formed as necessary in the amplifier structure disclosed in the present invention, as shown in fig. 3.