Topology optimization of a lithium niobate thin film y waveguide modulator and related components

Abstract

The application provides a topological optimization method of a lithium niobate thin film Y waveguide modulator and related components, including: controlling the material refractive index of the lithium niobate thin film Y waveguide modulator in a preset optimization region to continuously change and take values in a preset refractive index range to optimize the material refractive index of the lithium niobate thin film Y waveguide modulator; mapping the continuously changed and taken values of the material refractive index of the lithium niobate thin film Y waveguide modulator to a binary refractive index, the binary refractive index corresponding to the optimal material refractive index distribution of the lithium niobate thin film Y waveguide modulator; optimizing the curvature radius of the lithium niobate thin film Y waveguide modulator to obtain an optimized curvature radius value; and performing topological optimization design on the lithium niobate thin film Y waveguide modulator according to the optimal material refractive index distribution of the lithium niobate thin film Y waveguide modulator and the optimized curvature radius value. The method provided by the application realizes the design of a high-performance single-polarization lithium niobate thin film Y waveguide modulator.

Description

Technical Field

[0001] This invention relates to the fields of optical communication, optical computing and sensing technologies, and in particular to a topology optimization of a lithium niobate thin-film Y-waveguide modulator and related components. Background Technology

[0002] The concept of integrated optics is based on fabricating optical waveguide components on planar substrates using micro-etching technology. Similar to integrated electronics, it offers the potential to integrate several functions into a single optical path during mass production, while also facilitating miniaturization and reducing optical connections. Therefore, the use of multifunctional integrated optical devices has long been considered a promising technological approach for developing gyroscopes. The most typical example of an integrated optical device is the integrated optical modulator, also known as a Y-waveguide modulator. It integrates a beam splitter, polarizer, and phase modulator, possessing advantages such as large modulation bandwidth, high polarization extinction ratio, and high integration. It has been widely used in Mach-Zehnder interferometers, self-coherent optical gyroscopes, fiber optic gyroscopes, and quantum optical devices. The modulation principle of the Y-waveguide modulator is to apply an external electric field at the electrodes to change the refractive index of the waveguide. This causes a phase difference in the beam passing through the waveguide, thus achieving phase modulation of the beam. High polarization extinction ratio (single polarization operation) is crucial for end-coupled modulation devices. In end-coupled devices, alignment errors exist between the polarization axis of the polarization-maintaining fiber and the crystal orientation of the Y-waveguide modulator. These errors excite components with different polarizations within the waveguide, resulting in a low polarization extinction ratio. This degrades the modulator's efficiency or the sensing accuracy of the Sagnac effect in fiber optic gyroscopes. Previous solutions primarily relied on a high-precision six-axis alignment platform combined with transmission spectroscopy testing to ensure single polarization operation of the Y-waveguide modulator, followed by UV curing and encapsulation. However, this encapsulation method is cumbersome and difficult to mass-produce. Summary of the Invention

[0003] This invention provides a topology optimization and related components for a lithium niobate thin-film Y-waveguide modulator, which addresses the shortcomings of existing technologies such as low coupling alignment efficiency, complex steps, and poor repeatability. The structure of the lithium niobate thin-film Y-waveguide modulator is designed through a topology optimization method to achieve single-polarization transmission. Furthermore, the insertion loss of the lithium niobate thin-film Y-waveguide modulator is optimized by reverse design to achieve a high-performance lithium niobate thin-film Y-waveguide modulator operating in single polarization mode.

[0004] This invention provides a topology optimization method for a lithium niobate thin-film Y-waveguide modulator, comprising: controlling the material refractive index of the lithium niobate thin-film Y-waveguide modulator within a preset optimization region to continuously vary within a preset refractive index range to optimize the material refractive index of the lithium niobate thin-film Y-waveguide modulator; mapping the continuously varying material refractive index of the lithium niobate thin-film Y-waveguide modulator to a binary refractive index, the binary refractive index corresponding to the optimal material refractive index distribution of the lithium niobate thin-film Y-waveguide modulator; optimizing the radius of curvature of the lithium niobate thin-film Y-waveguide modulator to obtain an optimized radius of curvature value; and performing topology optimization design of the lithium niobate thin-film Y-waveguide modulator based on the optimal material refractive index distribution of the lithium niobate thin-film Y-waveguide modulator and the optimized radius of curvature value.

[0005] According to the present invention, a topology optimization method for a lithium niobate thin-film Y-waveguide modulator is provided, wherein the refractive index of the lithium niobate thin-film Y-waveguide modulator is continuously varied within a preset refractive index range to optimize the refractive index of the lithium niobate thin-film Y-waveguide modulator. The method includes: establishing objective functions for the height and width of the lithium niobate thin-film Y-waveguide modulator, and simultaneously optimizing the objective functions using a gradient descent algorithm to optimize the refractive index of the lithium niobate thin-film Y-waveguide modulator.

[0006] According to the present invention, a topology optimization method for a lithium niobate thin-film Y-waveguide modulator includes mapping the continuously varying refractive index of the lithium niobate thin-film Y-waveguide modulator to a binary refractive index. This includes: approximating the refractive index of the lithium niobate thin-film Y-waveguide modulator to a preset maximum or minimum value within a refractive index range using a Sigmoid function; and mapping the minimum and maximum values ​​using a step function to obtain the binary refractive index. The Sigmoid function is:

[0007] ;

[0008] in, x The refractive index value is assigned to each point within the preset optimization region.

[0009] According to the present invention, a topology optimization method for a lithium niobate thin-film Y-waveguide modulator is provided. The optimization of the radius of curvature of the lithium niobate thin-film Y-waveguide modulator to obtain an optimized radius of curvature value includes: adding a structural penalty term to the objective function to obtain a penalty function; and using the penalty function to optimize the radius of curvature of the lithium niobate thin-film Y-waveguide modulator to obtain the optimized radius of curvature value.

[0010] The present invention also provides a lithium niobate thin film Y waveguide modulator according to the topology optimization method of the lithium niobate thin film Y waveguide modulator described above, comprising a substrate, a buried oxide layer, a lithium niobate layer and a cladding layer arranged sequentially from bottom to top, wherein a thin film Y waveguide is provided under the cladding layer and an electrode layer is provided on the cladding layer.

[0011] This invention also provides a method for fabricating a lithium niobate thin-film Y-waveguide modulator based on the topology optimization method for lithium niobate thin-film Y-waveguide modulators described above, comprising:

[0012] Step 1: Deposit a buried oxide layer on the substrate;

[0013] Step 2: Prepare a lithium niobate layer on the sample obtained in Step 1;

[0014] Step 3: Prepare a transfer etching pattern on the sample obtained in Step 2 using EB exposure;

[0015] Step 4: Deposit a Cr layer on the sample obtained in Step 3;

[0016] Step 5: Remove the transfer etching pattern and the Cr layer on the transfer etching pattern from the sample obtained in step 4;

[0017] Step 6: ICP etching is performed on the sample obtained in step 5 to remove the lithium niobate layer and the remaining portion of the Cr layer covering it.

[0018] Step 7: Remove the Cr layer from the sample obtained in Step 6 using a grinding and polishing process;

[0019] Step 8: PECVD deposit a SiO2 layer on the sample obtained in step 7;

[0020] Step 9: A polished end face is made on the sample obtained in step 8 using a grinding and polishing process;

[0021] Step 10: Deposit an electrode layer onto the sample obtained in step 9 by sputtering or vapor deposition to complete the fabrication of the lithium niobate thin film Y-waveguide modulator.

[0022] This invention also provides a topology optimization device for a lithium niobate thin-film Y-waveguide modulator, comprising: a control unit for controlling the refractive index of the material of the lithium niobate thin-film Y-waveguide modulator within a preset optimization region to continuously vary within a preset refractive index range to optimize the refractive index of the material of the lithium niobate thin-film Y-waveguide modulator; a binary unit for mapping the continuously varying refractive index of the material of the lithium niobate thin-film Y-waveguide modulator to a binary refractive index, wherein the binary refractive index corresponds to the optimal material refractive index distribution of the lithium niobate thin-film Y-waveguide modulator; an optimization unit for optimizing the radius of curvature of the lithium niobate thin-film Y-waveguide modulator to obtain an optimized radius of curvature value; and a design unit for performing topology optimization design of the lithium niobate thin-film Y-waveguide modulator based on the optimal material refractive index distribution and the optimized radius of curvature value.

[0023] The present invention also provides an electronic device, including a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor executes the program to implement the topology optimization method for the lithium niobate thin-film Y-waveguide modulator as described above.

[0024] The present invention also provides a non-transitory computer-readable storage medium having a computer program stored thereon, which, when executed by a processor, implements a topology optimization method for a lithium niobate thin-film Y-waveguide modulator as described above.

[0025] The present invention also provides a computer program product, including a computer program that, when executed by a processor, implements a topology optimization method for a lithium niobate thin-film Y-waveguide modulator as described above.

[0026] This invention provides a topology optimization method and related components for a lithium niobate thin-film Y-waveguide modulator, comprising: controlling the material refractive index of the lithium niobate thin-film Y-waveguide modulator to continuously vary within a preset refractive index range to optimize the material refractive index of the lithium niobate thin-film Y-waveguide modulator; mapping the continuously varying material refractive index of the lithium niobate thin-film Y-waveguide modulator to a binary refractive index, the binary refractive index corresponding to the optimal material refractive index distribution of the lithium niobate thin-film Y-waveguide modulator; optimizing the radius of curvature of the lithium niobate thin-film Y-waveguide modulator to obtain an optimized radius of curvature value; and performing topology optimization design of the lithium niobate thin-film Y-waveguide modulator based on the optimal material refractive index distribution and the optimized radius of curvature value. This invention designs the structure of the lithium niobate thin-film Y-waveguide modulator through topology optimization, achieving single-polarization transmission of the lithium niobate thin-film Y-waveguide modulator, and combines this with reverse design to optimize the insertion loss of the lithium niobate thin-film Y-waveguide modulator to achieve a high-performance single-polarization lithium niobate thin-film Y-waveguide modulator. Attached Figure Description

[0027] To more clearly illustrate the technical solutions in this invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0028] Figure 1 This is a flowchart illustrating a topology optimization method for a lithium niobate thin-film Y-waveguide modulator provided by the present invention.

[0029] Figure 2 This is a top view of a lithium niobate thin-film Y-waveguide modulator provided by the present invention;

[0030] Figure 3 This is a schematic diagram of the optical field distribution of a lithium niobate thin-film Y-waveguide modulator provided by the present invention;

[0031] Figure 4 This is a schematic diagram illustrating the variation trend of the equivalent refractive index in TE / TM mode with height and width provided by the present invention;

[0032] Figure 5 This is a schematic diagram illustrating the variation trend of TE / TM mode loss with height and width provided by the present invention;

[0033] Figure 6 This is a schematic diagram of the TM mode light field propagation with a width of 750nm and a height of 300nm provided by the present invention;

[0034] Figure 7 This is a schematic diagram of TE mode light field propagation with a width of 750nm and a height of 300nm provided by the present invention;

[0035] Figure 8 This is a schematic diagram of TM mode transmission transmittance within a length range of 20 micrometers provided by the present invention;

[0036] Figure 9 This is a schematic diagram of TE mode transmission transmittance within a length range of 20 micrometers provided by the present invention;

[0037] Figure 10 This is a schematic diagram of a method for fabricating a lithium niobate thin-film Y-waveguide modulator provided by the present invention;

[0038] Figure 11 This is a schematic diagram of the structure of the Mach-Zehnder modulator provided by the present invention;

[0039] Figure 12 This is a schematic diagram of the topology optimization device for a lithium niobate thin-film Y-waveguide modulator provided by the present invention;

[0040] Figure 13 This is a schematic diagram of the structure of the electronic device provided by the present invention. Detailed Implementation

[0041] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this invention. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0042] The following is combined with Figures 1-13 This invention describes a topology optimization method and related components for a lithium niobate thin-film Y-waveguide modulator.

[0043] Please refer to Figure 1 , Figure 1 This is a schematic flowchart illustrating a topology optimization method for a lithium niobate thin-film Y-waveguide modulator provided by the present invention.

[0044] Please refer to Figure 2 , Figure 2 This is a top view of a lithium niobate thin-film Y-waveguide modulator provided by the present invention.

[0045] This invention provides a topology optimization method for a lithium niobate thin-film Y-waveguide modulator, comprising:

[0046] 101: The refractive index of the lithium niobate thin-film Y-waveguide modulator is controlled to continuously vary within a preset refractive index range within a preset optimization region in order to optimize the refractive index of the lithium niobate thin-film Y-waveguide modulator.

[0047] 102: The material refractive index of the continuously varying lithium niobate thin film Y-waveguide modulator is mapped to a binary refractive index, which corresponds to the optimal material refractive index distribution of the lithium niobate thin film Y-waveguide modulator.

[0048] 103: Optimize the radius of curvature of the lithium niobate thin-film Y-waveguide modulator to obtain the optimized radius of curvature value;

[0049] 104: The topology of the lithium niobate thin film Y-waveguide modulator is optimized based on the optimal material refractive index distribution and optimized radius of curvature value.

[0050] Y-waveguide modulators are key components in optoelectronic chips for distributing and combining beam paths, and are widely used in optical communication, optical computing, and sensing. Their function is to split an incident beam into two or more sub-beams of equal or different power. Y-waveguide modulators are required in Mach-Zehnder interferometers, self-coherent optical systems, fiber optic gyroscopes, and quantum optical devices. The performance indicators of Y-waveguide modulators mainly include insertion loss, beam splitting ratio, size, and polarization extinction ratio. A high polarization extinction ratio (single-polarization operation) is particularly important for end-coupled modulation devices. In end-coupled devices, alignment errors exist between the polarization axis of the polarization-maintaining fiber and the crystal orientation of the chip, which excites components with different polarizations in the waveguide. This degrades the efficiency of the modulator or the sensing accuracy of the Sagnac effect in fiber optic gyroscopes. Previous solutions primarily relied on a high-precision six-axis alignment platform combined with transmission spectroscopy testing to ensure single-polarization operation of the chip, followed by UV curing and encapsulation. This process was complex and lacked repeatability; the fabrication process was unstable, resulting in poor system reliability and hindering large-scale production.

[0051] To address the technical problems existing in the prior art, this invention provides a design method and structure for a single-polarization, low-insertion-loss Y-waveguide modulator on a thin-film lithium niobate platform. Compared with existing Y-waveguide modulator structures, it effectively reduces the performance degradation introduced by polarization. This invention has conducted corresponding verification simulations and proposed feasible process steps, making the fabrication of this structure possible. Specifically, from the top view of the lithium niobate thin-film Y-waveguide modulator, it can be seen that different gray values ​​represent the refractive index distribution, the Y-shaped region represents the refractive index of lithium niobate, and the remaining regions represent the cladding and substrate materials, which can be silicon dioxide. The left side of the device is the input port, and the right side is the output port after beam splitting. This patent designs the dimensions of the central Y-waveguide modulator and the waveguides on both the input and output sides. The waveguide structure is mainly designed based on its cutoff condition (single polarization characteristics), and the morphology of the central Y-waveguide modulator is a structure with low insertion loss obtained through topology optimization. The design of the Y-waveguide modulator is mainly achieved through topology optimization. The topology optimization process consists of three parts. First, after defining a preset optimization region, the refractive index within the preset optimization region can be continuously selected between the maximum and minimum refractive indices to perform grayscale optimization of the material refractive index of the lithium niobate thin-film Y-waveguide modulator. Second, the continuously varying material refractive index of the lithium niobate thin-film Y-waveguide modulator is mapped to a binary refractive index. The binary refractive index corresponds to the optimal material refractive index distribution of the lithium niobate thin-film Y-waveguide modulator, which can correspond to the refractive indices of the device layer material and the cladding material, respectively. Third, the radius of curvature of the lithium niobate thin-film Y-waveguide modulator is optimized to obtain a machinable structure with an optimized radius of curvature value within an acceptable range. The monolithically integrated beam splitter and modulation chip based on thin-film lithium niobate (LiNiO) utilizes a thin-film LiNiO platform, which facilitates device size reduction, integration, and miniaturization, thereby improving modulation efficiency. The fabrication of related devices based on the LiNiO platform employs semiconductor processes, a mature technology that significantly improves device stability and reliability. Furthermore, mature large-wafer products of LiNiO facilitate large-scale production and offer cost advantages. An on-chip polarizer is fabricated on the LiNiO platform for polarization control, improving the polarization extinction ratio of the integrated optical waveguide modulator, reducing polarization noise, and enhancing the measurement accuracy of the fiber optic gyroscope system, while also facilitating integration. Monolithically integrating the beam splitter, polarizer, and Y-branch phase modulator greatly enhances system stability and reliability. Thin-film LiNiO modulators, characterized by low modulation voltage, high modulation bandwidth, and low insertion loss, are expected to have significant potential applications in future optical communications.

[0052] Please refer to Figure 3 , Figure 3 A schematic diagram of the optical field distribution of a lithium niobate thin-film Y-waveguide modulator provided by the present invention.

[0053] Simulation of the optimization results shows that the optical field is well confined within the waveguide, and the beam splitting structure does not introduce excessive scattering loss. The main function here is the gradient structure inside the Y-waveguide modulator. Compared with the traditional linear or low-order polynomial gradient structure, the design in this patent has a higher degree of freedom, thus achieving better results. The simulation loss can be as low as 0.13dB.

[0054] In summary, the topology optimization method for lithium niobate thin-film Y-waveguide modulators provided by this invention achieves single-polarization transmission of the lithium niobate thin-film Y-waveguide modulator by designing its structure, effectively reducing the performance degradation introduced by polarization. Furthermore, by combining reverse design to optimize the insertion loss of the lithium niobate thin-film Y-waveguide modulator, a high-performance lithium niobate thin-film Y-waveguide modulator operating on a single polarization is achieved.

[0055] Based on the above embodiments:

[0056] As a preferred embodiment, the refractive index of the lithium niobate thin-film Y-waveguide modulator is controlled to continuously vary within a preset refractive index range within a preset optimization region to optimize the refractive index of the lithium niobate thin-film Y-waveguide modulator. This includes: establishing objective functions for the height and width of the lithium niobate thin-film Y-waveguide modulator, and simultaneously optimizing the objective functions using a gradient descent algorithm to optimize the refractive index of the lithium niobate thin-film Y-waveguide modulator.

[0057] As a preferred embodiment, mapping the refractive index of the continuously varying lithium niobate thin-film Y-waveguide modulator material to a binary refractive index includes: approximating the refractive index of the lithium niobate thin-film Y-waveguide modulator material to a preset maximum or minimum value within a refractive index range using a Sigmoid function; and mapping the minimum and maximum values ​​using a step function to obtain the binary refractive index. The Sigmoid function is:

[0058] ;

[0059] in, x The refractive index value is set for each point within the preset optimization region.

[0060] As a preferred embodiment, optimizing the radius of curvature of the lithium niobate thin-film Y-waveguide modulator to obtain an optimized radius of curvature value includes: adding a structural penalty term to the objective function to obtain a penalty function; and using the penalty function to optimize the radius of curvature of the lithium niobate thin-film Y-waveguide modulator to obtain an optimized radius of curvature value.

[0061] Please refer to Figure 4 , Figure 4 This is a schematic diagram illustrating the variation trend of the equivalent refractive index of the TE / TM mode with height and width provided by the present invention.

[0062] Please refer to Figure 5 , Figure 5 This is a schematic diagram illustrating the variation trend of TE / TM mode loss with height and width provided by the present invention.

[0063] Please refer to Figure 6 , Figure 6 This is a schematic diagram of the propagation of the TM mode light field with a width of 750nm and a height of 300nm, provided for the present invention.

[0064] Please refer to Figure 7 , Figure 7 This is a schematic diagram of TE mode light field propagation with a width of 750nm and a height of 300nm, provided for the present invention.

[0065] Please refer to Figure 8 , Figure 8 This is a schematic diagram of the TM mode transmission transmittance over a length range of 20 micrometers, provided by the present invention.

[0066] Please refer to Figure 9 , Figure 9 This is a schematic diagram of TE mode transmission transmittance within a length range of 20 micrometers, provided by the present invention.

[0067] The design of the single-polarization lithium niobate thin-film Y-waveguide modulator structure is mainly achieved by adjusting the height and width of the waveguide. Simultaneously, the thickness of the top silicon dioxide layer needs to be changed to allow TM mode leakage. The design already considers the waveguide sidewall tilt caused by the manufacturing process, approximately 70°. After parameter scanning, single-polarization operation can be achieved within a certain waveguide size range. As the waveguide width and height decrease, TM mode cutoff occurs when TE mode can still transmit effectively (equivalent refractive index is 0). These structural parameters correspond to single-mode operation conditions, and the same trend can be observed from the loss characteristics. Figure 5 The lower center shows a loss of 0 because the loss is too high to calculate for both TE and TM modes (the actual loss should be infinite). Taking a width of 750nm and a height of 300nm as an example, this structure effectively confines the TE mode, while the TM mode gradually leaks during transmission. Within a 20-micron length, the average transmittance of TM is 0.106 (-9.74dB), and the transmittance of TE is 0.922 (-0.354dB). In fiber optic gyroscopes, the Y-waveguide needs to function as a polarizer. Waveguides etched with lithium niobate thin films have dual polarization modes, allowing simultaneous transmission of both TE and TM modes. However, for X-cut Y-waveguides transmitting lithium niobate thin films, only the TE mode needs to be transmitted. Therefore, a filter to remove the TM mode is required to achieve single-polarization operation.

[0068] Please refer to Figure 10 , Figure 10This is a schematic diagram illustrating a method for fabricating a lithium niobate thin-film Y-waveguide modulator provided by the present invention.

[0069] Please refer to Figure 11 , Figure 11 This is a schematic diagram of the structure of the Mach-Zehnder modulator provided by the present invention.

[0070] This invention also provides a lithium niobate thin-film Y-waveguide modulator based on the above-described topology optimization method for lithium niobate thin-film Y-waveguide modulators, comprising a substrate, a buried oxide layer, a lithium niobate layer, and a cladding layer arranged sequentially from bottom to top. A thin-film Y-waveguide is provided under the cladding layer, and an electrode layer is provided on the cladding layer. The buried oxide layer and the cladding layer can be made of SiO2.

[0071] This structure can be used in Y-waveguide fiber optic gyroscopes because the accuracy of fiber optic gyroscopes is very sensitive to stray polarization in the device. The device designed in this invention can achieve more than 35 dB of stray polarization component suppression within a length of 75 micrometers. Simulations show that the total insertion loss of the device can be less than 3 dB (coupling loss, beam splitter loss, and waveguide transmission loss).

[0072] This invention also provides a method for fabricating a lithium niobate thin-film Y-waveguide modulator based on the above-described topology optimization method for lithium niobate thin-film Y-waveguide modulators, comprising:

[0073] Step 1: Deposit a buried oxide layer on the substrate;

[0074] Step 2: Prepare a lithium niobate layer on the sample obtained in Step 1;

[0075] Step 3: Prepare a transfer etching pattern on the sample obtained in Step 2 using EB (electron beam lithography);

[0076] Step 4: Deposit a Cr layer on the sample obtained in Step 3;

[0077] Step 5: Remove the transfer etched pattern and the Cr layer on the transfer etched pattern from the sample obtained in step 4;

[0078] Step 6: ICP (Inductively Coupled Plasma Etching) is used to remove the lithium niobate layer from the sample obtained in Step 5, and to remove the remaining parts of the Cr layer covering the top.

[0079] Step 7: Remove the Cr layer from the sample obtained in Step 6 using a grinding and polishing process;

[0080] Step 8: PECVD deposit a SiO2 layer on the sample obtained in step 7;

[0081] Step 9: A polished end face is made on the sample obtained in step 8 using a grinding and polishing process;

[0082] Step 10: Deposit an electrode layer onto the sample obtained in step 9 by sputtering or vapor deposition to complete the fabrication of the lithium niobate thin film Y-waveguide modulator.

[0083] In a lithium niobate thin-film Y-waveguide modulator, a ridged TFLN (thin-film lithium niobate) waveguide is formed from an LN (lithium niobate) layer using photolithography. Benefiting from the refractive index difference between LN and silicon dioxide, the light field can propagate through the TFLN via total internal reflection. Metal electrodes are arranged on both sides of the TFLN waveguide, and a transverse electric field can be generated in the waveguide region by applying a voltage. According to the linear electro-optic effect of LN, when an electric field is applied, it will cause a significant change in the refractive index of the LN material, significantly altering the effective refractive index of the optical mode, and thus directly affecting the phase of the optical signal in the waveguide. To improve the conversion efficiency from electrical to optical signals, the distance between the metal electrodes is usually reduced to enhance the electric field. However, metal electrodes have a strong light absorption effect to absorb leaked light, further filtering it out and improving the single polarization characteristics of the device. If the distance between the metal electrodes is too close, there will be a large spatial overlap between the metal electrodes and the optical mode field, significantly increasing the optical signal loss. The thickness of the cladding needs to be appropriate. If the cladding is too thick, a large portion of the optical field may be confined within the cladding, reducing the optical field distribution within the waveguide core and decreasing the spatial overlap efficiency between the optical field and the LN material, thereby reducing the modulation efficiency of the Y waveguide modulator. If the cladding is too thin, the optical field area may be too large, resulting in excessive optical loss.

[0084] Please refer to Figure 12 , Figure 12 This is a schematic diagram of the topology optimization device for a lithium niobate thin-film Y-waveguide modulator provided by the present invention.

[0085] The present invention also provides a topology optimization device for a lithium niobate thin-film Y-waveguide modulator, comprising: a control unit 1201, used to control the refractive index of the material of the lithium niobate thin-film Y-waveguide modulator within a preset optimization region to continuously vary within a preset refractive index range to optimize the refractive index of the material of the lithium niobate thin-film Y-waveguide modulator; a binary unit 1202, used to map the continuously varying refractive index of the material of the lithium niobate thin-film Y-waveguide modulator to a binary refractive index, wherein the binary refractive index corresponds to the optimal material refractive index distribution of the lithium niobate thin-film Y-waveguide modulator; an optimization unit 1203, used to optimize the radius of curvature of the lithium niobate thin-film Y-waveguide modulator to obtain an optimized radius of curvature value; and a design unit 1204, used to perform topology optimization design of the lithium niobate thin-film Y-waveguide modulator based on the optimal material refractive index distribution and the optimized radius of curvature value of the lithium niobate thin-film Y-waveguide modulator.

[0086] For a description of the topology optimization device for a lithium niobate thin-film Y-waveguide modulator provided by the present invention, please refer to the above method embodiments; the present invention will not be described again here.

[0087] Figure 13 An example is a schematic diagram of the physical structure of an electronic device, such as... Figure 13 As shown, the electronic device may include: a processor 1301, a communications interface 1302, a memory 1303, and a communications bus 1304, wherein the processor 1301, the communications interface 1302, and the memory 1303 communicate with each other through the communications bus 1304. The processor 1301 can call logic instructions in the memory 1303 to execute a topology optimization method for a lithium niobate thin-film Y-waveguide modulator. This method includes: controlling the material refractive index of the lithium niobate thin-film Y-waveguide modulator within a preset optimization region to continuously vary within a preset refractive index range to optimize the material refractive index of the lithium niobate thin-film Y-waveguide modulator; mapping the continuously varying material refractive index of the lithium niobate thin-film Y-waveguide modulator to a binary refractive index, the binary refractive index corresponding to the optimal material refractive index distribution of the lithium niobate thin-film Y-waveguide modulator; optimizing the radius of curvature of the lithium niobate thin-film Y-waveguide modulator to obtain an optimized radius of curvature value; and performing topology optimization design on the lithium niobate thin-film Y-waveguide modulator based on the optimal material refractive index distribution and the optimized radius of curvature value.

[0088] Furthermore, the logical instructions in the aforementioned memory 1303 can be implemented as software functional units and, when sold or used as independent products, can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of the present invention, or the part that contributes to the prior art, or a part of the technical solution, can be embodied in the form of a software product. This computer software product is stored in a storage medium and includes several instructions to cause a computer device (which may be a personal computer, server, or network device, etc.) to execute all or part of the steps of the methods described in the various embodiments of the present invention. The aforementioned storage medium includes various media capable of storing program code, such as USB flash drives, portable hard drives, read-only memory (ROM), random access memory (RAM), magnetic disks, or optical disks.

[0089] On the other hand, the present invention also provides a computer program product, which includes a computer program that can be stored on a non-transitory computer-readable storage medium. When the computer program is executed by a processor, the computer can execute the topology optimization method for a lithium niobate thin-film Y-waveguide modulator provided by the above methods. The method includes: controlling the material refractive index of the lithium niobate thin-film Y-waveguide modulator within a preset optimization region to continuously vary within a preset refractive index range to optimize the material refractive index of the lithium niobate thin-film Y-waveguide modulator; mapping the continuously varying material refractive index of the lithium niobate thin-film Y-waveguide modulator to a binary refractive index, the binary refractive index corresponding to the optimal material refractive index distribution of the lithium niobate thin-film Y-waveguide modulator; optimizing the radius of curvature of the lithium niobate thin-film Y-waveguide modulator to obtain an optimized radius of curvature value; and performing topology optimization design of the lithium niobate thin-film Y-waveguide modulator based on the optimal material refractive index distribution and the optimized radius of curvature value.

[0090] In another aspect, the present invention also provides a non-transitory computer-readable storage medium storing a computer program thereon. When executed by a processor, the computer program implements a topology optimization method for a lithium niobate thin-film Y-waveguide modulator provided by the methods described above. This method includes: controlling the material refractive index of the lithium niobate thin-film Y-waveguide modulator within a preset optimization region to continuously vary within a preset refractive index range to optimize the material refractive index of the lithium niobate thin-film Y-waveguide modulator; mapping the continuously varying material refractive index of the lithium niobate thin-film Y-waveguide modulator to a binary refractive index, the binary refractive index corresponding to the optimal material refractive index distribution of the lithium niobate thin-film Y-waveguide modulator; optimizing the radius of curvature of the lithium niobate thin-film Y-waveguide modulator to obtain an optimized radius of curvature value; and performing topology optimization design on the lithium niobate thin-film Y-waveguide modulator based on the optimal material refractive index distribution and the optimized radius of curvature value.

[0091] The device embodiments described above are merely illustrative. The units described as separate components may or may not be physically separate. The components shown as units may or may not be physical units; that is, they may be located in one place or distributed across multiple network units. Some or all of the modules can be selected to achieve the purpose of this embodiment according to actual needs. Those skilled in the art can understand and implement this without any creative effort.

[0092] Through the above description of the embodiments, those skilled in the art can clearly understand that each embodiment can be implemented by means of software plus necessary general-purpose hardware platforms, and of course, it can also be implemented by hardware. Based on this understanding, the above technical solutions, in essence or the part that contributes to the prior art, can be embodied in the form of a software product. This computer software product can be stored in a computer-readable storage medium, such as ROM / RAM, magnetic disk, optical disk, etc., and includes several instructions to cause a computer device (which may be a personal computer, server, or network device, etc.) to execute the methods described in the various embodiments or some parts of the embodiments.

[0093] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A topology optimization method for a lithium niobate thin-film Y-waveguide modulator, characterized in that, include: The refractive index of the lithium niobate thin-film Y-waveguide modulator is continuously varied within a preset refractive index range to optimize the refractive index of the lithium niobate thin-film Y-waveguide modulator. The material refractive index of the continuously varying lithium niobate thin-film Y-waveguide modulator is mapped to a binary refractive index, which corresponds to the optimal material refractive index distribution of the lithium niobate thin-film Y-waveguide modulator. The radius of curvature of the lithium niobate thin-film Y-waveguide modulator was optimized to obtain an optimized radius of curvature value; Based on the optimal material refractive index distribution and the optimized radius of curvature value of the lithium niobate thin film Y waveguide modulator, the topology optimization design of the lithium niobate thin film Y waveguide modulator is performed; The refractive index of the lithium niobate thin-film Y-waveguide modulator, controlled within a preset optimization region, is continuously varied within a preset refractive index range to optimize the material refractive index of the lithium niobate thin-film Y-waveguide modulator, including: An objective function for the height and width of the lithium niobate thin-film Y-waveguide modulator is established, and the objective function is optimized by combining the gradient descent algorithm to optimize the material refractive index of the lithium niobate thin-film Y-waveguide modulator. Optimizing the radius of curvature of the lithium niobate thin-film Y-waveguide modulator to obtain an optimized radius of curvature value includes: A penalty function is obtained by adding a structural penalty term to the objective function; The radius of curvature of the lithium niobate thin-film Y-waveguide modulator is optimized using the penalty function to obtain an optimized radius of curvature value.

2. The topology optimization method for the lithium niobate thin-film Y-waveguide modulator according to claim 1, characterized in that, The process of mapping the refractive index of the continuously varying lithium niobate thin-film Y-waveguide modulator to a binary refractive index includes: The Sigmoid function is used to approximate the maximum or minimum value of the preset refractive index range of the material refractive index of the lithium niobate thin film Y waveguide modulator. The binary refractive index is obtained by mapping the minimum and maximum values ​​using a step function; The Sigmoid function is: ； in, x The refractive index value is assigned to each point within the preset optimization region.

3. A lithium niobate thin-film Y-waveguide modulator according to any one of claims 1 to 2, characterized in that, It includes a substrate, a buried oxide layer, a lithium niobate layer and a cladding layer arranged sequentially from bottom to top. A thin-film Y-waveguide is provided under the cladding layer and an electrode layer is provided on the cladding layer.

4. A method for fabricating a lithium niobate thin-film Y-waveguide modulator according to a topology optimization method for a lithium niobate thin-film Y-waveguide modulator as described in any one of claims 1 to 2, characterized in that, include: Step 1: Deposit a buried oxide layer on the substrate; Step 2: Prepare a lithium niobate layer on the sample obtained in Step 1; Step 3: Prepare a transfer etching pattern on the sample obtained in Step 2 using EB exposure; Step 4: Deposit a Cr layer on the sample obtained in Step 3; Step 5: Remove the transfer etching pattern and the Cr layer on the transfer etching pattern from the sample obtained in step 4; Step 6: ICP etching is performed on the sample obtained in step 5 to remove the lithium niobate layer and the remaining portion of the Cr layer covering it. Step 7: Remove the Cr layer from the sample obtained in Step 6 using a grinding and polishing process; Step 8: PECVD deposit a SiO2 layer on the sample obtained in step 7; Step 9: A polished end face is made on the sample obtained in step 8 using a grinding and polishing process; Step 10: Deposit an electrode layer onto the sample obtained in step 9 by sputtering or vapor deposition to complete the fabrication of the lithium niobate thin film Y-waveguide modulator.

5. A topology optimization device for a lithium niobate thin-film Y-waveguide modulator, characterized in that, The apparatus is used to implement the topology optimization method for the lithium niobate thin-film Y-waveguide modulator as described in any one of claims 1 to 2; the apparatus comprises: The control unit is used to control the refractive index of the material of the lithium niobate thin film Y waveguide modulator within a preset optimization region to continuously change within a preset refractive index range in order to optimize the refractive index of the material of the lithium niobate thin film Y waveguide modulator. A binary unit is used to map the material refractive index of the continuously varying lithium niobate thin-film Y-waveguide modulator to a binary refractive index, which corresponds to the optimal material refractive index distribution of the lithium niobate thin-film Y-waveguide modulator. The optimization unit is used to optimize the radius of curvature of the lithium niobate thin-film Y-waveguide modulator to obtain an optimized radius of curvature value. The design unit is used to perform topology optimization design of the lithium niobate thin film Y waveguide modulator based on the optimal material refractive index distribution and the optimized radius of curvature value of the lithium niobate thin film Y waveguide modulator.

6. An electronic device comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, characterized in that, When the processor executes the program, it implements the topology optimization method for the lithium niobate thin-film Y-waveguide modulator as described in any one of claims 1 to 2.

7. A non-transitory computer-readable storage medium having a computer program stored thereon, characterized in that, When the computer program is executed by the processor, it implements the topology optimization method for the lithium niobate thin-film Y-waveguide modulator as described in any one of claims 1 to 2.

8. A computer program product, comprising a computer program, characterized in that, When the computer program is executed by the processor, it implements the topology optimization method for the lithium niobate thin-film Y-waveguide modulator as described in any one of claims 1 to 2.

Images