Polarization-insensitive arrayed waveguide grating structure and design method thereof

Abstract

The present application relates to the field of on-chip waveguide spectrum splitting technology, and particularly to a polarization-insensitive arrayed waveguide grating structure and a design method thereof. The structure comprises an input end waveguide, an input slab waveguide, an array waveguide, an output slab waveguide and an output end waveguide connected in sequence along the light propagation direction; the array waveguide comprises a plurality of strip waveguides, and the adjacent strip waveguides have a preset optical path difference; the input end waveguide, the strip waveguide and the output end waveguide all adopt a vertical coupling double-core three-layer waveguide structure. By introducing the double-core three-layer waveguide structure, the light field coupling effect formed by the two high refractive index waveguide core layers and the intermediate low refractive index isolation layer is utilized to regulate the electromagnetic field distribution of the TE mode and the TM mode in the waveguide cross section, and then the effective refractive index and the group refractive index of different polarization modes are adjusted, the phase consistency of the TE mode and the TM mode is ensured, and on the premise of maintaining the compact size of the device, the performance targets of low insertion loss, high spectral resolution and polarization insensitivity are achieved.

Description

Technical Field

[0001] This invention relates to the field of on-chip waveguide spectral dispersive technology, specifically to a polarization-insensitive arrayed waveguide grating (AWG) structure and its design method. Background Technology

[0002] The development of integrated photonics technology has driven the iteration of traditional large-volume spectrometers towards on-chip integration. By implementing spectral splitting functions on photonic integration platforms such as silicon-based, silicon nitride, or silicon dioxide, the size, weight, and power consumption of the system can be significantly reduced, thereby meeting the demands for miniaturized optical systems in applications such as space remote sensing, environmental monitoring, and portable spectral detection. Arrayed waveguide gratings, as the current mainstream waveguide-type spectral splitting devices, utilize the fixed optical path difference between adjacent arrayed waveguides to cause interference of light of different wavelengths in the free propagation region (FPR) and focus it to different output ports, thus achieving wavelength spatial separation. They are widely used in on-chip spectrometer systems due to their easy expansion of channel number, high integration density, and good process compatibility. However, in practical integrated photonic platforms, the optical field in the waveguide typically propagates in transverse electric mode (TE mode) and transverse magnetic mode (TM mode). Due to the difference in transverse and longitudinal boundary conditions of the waveguide, the effective refractive index and group refractive index corresponding to the two polarization modes differ significantly. This difference accumulates and amplifies over long distances in arrayed waveguides, leading to inconsistent phase responses under different polarization states. This results in problems such as output channel center wavelength drift, abnormal spectral line broadening, and increased channel crosstalk, manifesting as the device's polarization sensitivity. This is particularly problematic in passive detection scenarios like Earth observation and atmospheric remote sensing, where the polarization state of incident light is completely random after multiple scatterings. Failure to address this issue will directly reduce the accuracy of spectral reconstruction and compromise the reliability of quantitative signal analysis.

[0003] To address the polarization sensitivity of AWGs, existing technologies have proposed various improvement schemes. These include introducing polarization beamsplitters or polarization rotators to convert different polarization states into a unified polarization state before transmission; optimizing the waveguide cross-section structure by employing near-square symmetrical waveguide sections; and using wide waveguides or weakly constrained waveguide structures to reduce mode constraint strength. However, these schemes still have significant limitations: introducing polarization beamsplitters / rotators increases insertion loss, significantly increasing device structural complexity and packaging difficulty, which is detrimental to high-density on-chip integration; using near-square symmetrical waveguide sections requires extremely high structural symmetry and usually leads to increased waveguide size, which occupies more chip area and raises processing thresholds and manufacturing costs; schemes relying on wide waveguides or weakly constrained waveguides require greater waveguide thickness, easily causing a surge in bending loss, making them completely unsuitable for on-chip spectrometer systems with extremely high size sensitivity.

[0004] Therefore, there is an urgent need to develop a polarization-insensitive arrayed waveguide grating structure and its design method that can achieve phase consistency control of TE mode and TM mode in the propagation path of the arrayed waveguide grating structure while maintaining a compact device size. Summary of the Invention

[0005] The purpose of this invention is to provide a polarization-insensitive arrayed waveguide grating structure that utilizes the vertical direction of a dual-core, three-layer waveguide to simultaneously and tunably compensate for the effective refractive index and group refractive index difference in TE and TM modes, thereby obtaining stable polarization-insensitive operating characteristics.

[0006] To achieve the above objectives, the present invention provides the following technical solution: a polarization-insensitive arrayed waveguide grating structure, comprising an input waveguide, an input planar waveguide, an arrayed waveguide, an output planar waveguide, and an output waveguide connected sequentially along the light propagation direction; The array waveguide includes multiple strip waveguides, and there is a preset optical path difference between adjacent strip waveguides; The input waveguide, each of the waveguides, and the output waveguide all adopt a vertically coupled dual-core three-layer waveguide structure. The dual-core three-layer waveguide structure includes, along its thickness direction, a first waveguide core layer, an isolation layer, and a second waveguide core layer. The refractive indices of the first and second waveguide core layers are both greater than the refractive index of the isolation layer, so that a vertical dual-core optical field coupling structure is formed between the first and second waveguide core layers. The first waveguide core layer, the isolation layer, and the second waveguide core layer have preset refractive indices and size parameters, so that the effective refractive index difference and group refractive index difference of TE mode or TM mode during propagation in the arrayed waveguide grating structure satisfy the polarization phase compensation condition, thereby achieving polarization-insensitive spectral separation.

[0007] Furthermore, in the dual-core three-layer waveguide structure, the first waveguide core layer and the second waveguide core layer are made of high refractive index waveguide material, and their thicknesses are both any value between 200nm and 800nm. The isolation layer is made of low refractive index dielectric material, and its thickness is any value between 5nm and 50nm. The high-refractive-index waveguide material includes at least one of Si and Si3N4; the low-refractive-index dielectric material includes SiO2.

[0008] Furthermore, each of the waveguides is designed as a ridge-type dual-core three-layer waveguide structure or a strip-type dual-core three-layer waveguide structure, and the length difference between two adjacent waveguides is the same to form a fixed optical path difference.

[0009] Furthermore, the waveguide is a ridge-type dual-core three-layer waveguide structure; In the waveguide, the second waveguide core layer has a protruding ridge waveguide, the height of which is 0.75-0.95 times the thickness of the second waveguide core layer, and the width is any value between 650nm and 950nm; the isolation layer and the first waveguide core layer are sequentially disposed on the ridge waveguide along the thickness direction, and the widths of the first waveguide core layer and the isolation layer are matched with the width of the ridge waveguide.

[0010] Furthermore, the strip waveguide design is a strip-shaped dual-core three-layer waveguide structure; In the waveguide, the first waveguide core layer, the isolation layer, and the second waveguide core layer are stacked sequentially along the thickness direction, and all three have the same width, which is any value between 650nm and 950nm.

[0011] Furthermore, the input planar waveguide includes an incident arc surface and an exit arc surface; the radius of the circle corresponding to the exit arc surface is any value between 30μm and 150μm, and the ratio of the radius of the circle corresponding to the exit arc surface to the radius of the circle corresponding to the incident arc surface is any value between 1.8 and 2.2. The output planar waveguide has the same structure as the input planar waveguide and is symmetrically arranged relative to the array waveguide.

[0012] Furthermore, the input planar waveguide and the output planar waveguide adopt a dual-core three-layer waveguide structure.

[0013] Furthermore, the input waveguide includes at least one input strip waveguide, and the input strip waveguide adopts a dual-core three-layer waveguide structure of the same type as the strip waveguide, so as to realize mode matching of the input optical signal between the input waveguide and the array waveguide; The output waveguide includes multiple output strip waveguides, and the output strip waveguides adopt the same type of dual-core three-layer waveguide structure as the strip waveguides. Multiple output strip waveguides are arranged along the arc surface of the output planar waveguide, and are used to couple and output optical signals of different wavelengths after being focused by the output planar waveguide.

[0014] This application provides a design method for the above-mentioned arrayed waveguide grating structure, including the following steps: S1. Based on the arrayed waveguide grating structure satisfying the Loland circular grating beam splitting principle, establish the optical path difference relationship between adjacent waveguides: , In the formula, It is the effective refractive index corresponding to the TE mode or TM mode in the arrayed waveguide region. It is the length difference between adjacent waveguides in the arrayed waveguide region. It is the center-to-center spacing between adjacent waveguides in the arrayed waveguide region. This refers to the effective refractive index corresponding to the TE or TM mode in the planar waveguide region, where the planar waveguide region includes both the input and output planar waveguide regions. It is the angle between the central axis of any input strip waveguide on the incident end arc surface of the input planar waveguide and the central axis of the incident end arc surface. is the angle between the central axis of any output strip waveguide on the arc surface of the output planar waveguide and the central axis of the arc surface of the output end; m is the grating order of the array waveguide grating structure; and λ is the center wavelength of the incident light. S2. Based on the optical path difference formula, establish the transmission phases corresponding to the TE mode or TM mode in the arrayed waveguide region and the planar waveguide region, respectively, and establish the total transmission phase of the TE mode or TM mode in the arrayed waveguide region and the planar waveguide region. The expression is: , In the formula, The propagation constant corresponding to the TE mode or TM mode in the arrayed waveguide region; c is the frequency of the optical signal; c is the speed of light in a vacuum. The transmission phase corresponding to the TE mode or TM mode in the region of the array waveguide (30) The transmission phase corresponding to the TE mode or TM mode in the planar waveguide region; Deploying the wavelet within the target operating band, the transmission phase expressions for TE mode or TM mode in the arrayed waveguide region and the planar waveguide region are obtained as follows: , , In the formula, This represents frequency variation terms of third order and above. The center frequency of the target operating band; The group refractive index corresponding to the TE mode or TM mode in the arrayed waveguide region. It is the group refractive index corresponding to the TE mode or TM mode in the planar waveguide region; S3. Based on the expression for the total transmission phase, establish a polarization phase mismatch model between the TE mode and the TM mode within the same spectral channel, and decompose it into a fixed polarization phase offset term. With polarization phase drift term ; The transmission phase difference between TE mode and TM mode The expression is: , in, , , , ; The fixed polarization phase offset term The expression is: , The polarization phase drift term The expression is: , In the formula, The effective refractive index difference between the TE mode and the TM mode in the array waveguide region. The group refractive index difference between the TE and TM modes in the array waveguide region. The effective refractive index difference between the TE mode and the TM mode in the planar waveguide region. The group refractive index difference between the TE mode and the TM mode in the planar waveguide region; S4. Adjust the structural parameters of the strip waveguide in the arrayed waveguide region, and the structural parameters of the input strip waveguide and output strip waveguide in the planar waveguide region, so that the polarization phase shift term... Polarization phase drift term It also meets the preset polarization compensation conditions.

[0015] Furthermore, the preset polarization phase compensation condition includes a fixed polarization phase offset term. And polarization phase drift term .

[0016] The beneficial effects of this invention are as follows: The polarization-insensitive arrayed waveguide grating structure provided in this application, by introducing a dual-core, three-layer waveguide structure, can utilize the optical field coupling effect formed by the upper and lower high-refractive-index waveguide core layers and the middle low-refractive-index isolation layer to regulate the electromagnetic field distribution of TE and TM modes within the waveguide cross-section. This, in turn, adjusts the effective refractive index and group refractive index corresponding to different polarization modes, thereby compensating for polarization-related phase errors in the propagation path of the arrayed waveguide grating and ensuring phase consistency between the TE and TM modes. This arrayed waveguide grating structure eliminates the need for additional polarization processing units such as polarization beamsplitters and polarization rotators, enabling wavelength overlap of different polarization states at the output channel. While maintaining a compact device size, it simultaneously achieves low insertion loss, high spectral resolution, and polarization insensitivity, avoiding the problems of additional insertion loss, increased structural complexity, and increased packaging difficulty introduced by traditional polarization compensation schemes. This significantly improves the integration and operational stability of on-chip spectral splitting devices.

[0017] By adjusting the structure, thickness, width, and other structural parameters of the high-refractive-index waveguide core layer and the low-refractive-index isolation layer, the array waveguide grating structure can be adapted to design requirements such as different spectral resolutions and operating bandwidths, and is compatible with various integrated photonic material platforms such as silicon-based, silicon nitride, and silicon dioxide, thereby improving the design flexibility and process compatibility of the array waveguide grating structure.

[0018] The design method for polarization-insensitive arrayed waveguide grating structures provided in this application establishes a polarization mismatch model based on the total transmission phase difference between the TE and TM modes in the arrayed waveguide grating, decomposing the phase error caused by polarization into a fixed polarization phase offset term. and the polarization phase drift term that varies with frequency The structural parameters of the arrayed waveguide region and the planar waveguide region were optimized in a directional manner to meet the polarization phase compensation conditions. This actively suppressed polarization sensitivity at the theoretical model level, significantly improving the accuracy and repeatability of the structural design. In other words, this design method can simultaneously suppress the polarization sensitivity of the arrayed waveguide grating from two dimensions: the intrinsic waveguide structure and the phase transmission mechanism. While ensuring compact device size, low insertion loss, and high integration, it achieves stable and reliable polarization-insensitive spectral splitting, making the arrayed waveguide grating structure suitable for applications requiring high integration, such as on-chip micro-spectroscopy, integrated photonic spectral sensing, and space remote sensing.

[0019] The above description is merely an overview of the technical solution of the present invention. In order to better understand the technical means of the present invention and to implement it in accordance with the contents of the specification, the preferred embodiments of the present invention are described in detail below with reference to the accompanying drawings. Attached Figure Description

[0020] Figure 1 This is a three-dimensional schematic diagram of a polarization-insensitive arrayed waveguide grating structure according to an embodiment of the present invention; Figure 2 This is a three-dimensional schematic diagram of a ridge-type dual-core three-layer waveguide structure according to an embodiment of the present invention; Figure 3 This is a cross-sectional view along the width direction of a ridge-type dual-core three-layer waveguide structure according to an embodiment of the present invention; Figure 4 This is a three-dimensional schematic diagram of a strip-shaped dual-core three-layer waveguide structure according to an embodiment of the present invention; Figure 5 This is a cross-sectional view along the width direction of a strip-shaped dual-core three-layer waveguide structure according to an embodiment of the present invention; Figure 6 This is a schematic diagram of the input strip waveguide structure according to an embodiment of the present invention; Figure 7 The above are the performance test results of the polarization-insensitive arrayed waveguide grating structure shown in Embodiment 1 of the present invention. Figure 8 The above are the performance test results of the polarization-insensitive arrayed waveguide grating structure shown in Embodiment 2 of the present invention. Figure label: 1. Input waveguide; 11. Input strip waveguide; 2. Input planar waveguide; 30. Arrayed waveguide; 3. Strip waveguide; 4. Output planar waveguide; 5. Output waveguide; 51. Output strip waveguide; 6. Substrate layer; 31. First waveguide core layer; 32. Isolation layer; 33. Second waveguide core layer. Detailed Implementation

[0021] The technical solutions of the present invention will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention. Furthermore, the technical features involved in the different embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0022] like Figure 1As shown, a preferred embodiment of this application provides a polarization-insensitive arrayed waveguide grating structure. This polarization-insensitive arrayed waveguide grating structure includes an input waveguide 1, an input planar waveguide 2, an arrayed waveguide 30, an output planar waveguide 4, and an output waveguide 5, connected sequentially along the light propagation direction. The arrayed waveguide 30 includes multiple waveguides 3, with a preset optical path difference between adjacent waveguides 3. The input waveguide 1, each waveguide 3, and the output waveguide 5 all employ a vertically coupled dual-core three-layer waveguide structure. This dual-core three-layer waveguide structure includes, along its thickness direction, a first waveguide core layer 31, an isolation layer 32, and a second waveguide core layer 33. The refractive indices of both the first waveguide core layer 31 and the second waveguide core layer 33 are greater than the refractive index of the isolation layer 32, thereby forming a vertical dual-core optical field coupling structure between the first waveguide core layer 31 and the second waveguide core layer 33. The first waveguide core layer 31, the isolation layer 32, and the second waveguide core layer 33 have preset refractive index and size parameters, so that the effective refractive index difference and group refractive index difference between the TE mode and the TM mode during the propagation process of the arrayed waveguide grating structure meet the polarization phase compensation condition, thereby reducing the phase difference between the TE mode and the TM mode during the transmission process of the arrayed waveguide grating structure, and thus enabling optical signals of different polarization states to be focused at the same wavelength position in the same output channel, achieving polarization-insensitive spectral separation. This embodiment introduces a vertically coupled dual-core three-layer waveguide structure into the arrayed waveguide grating structure, enabling vertical optical field coupling between the first waveguide core layer 31 and the second waveguide core layer 33. Simultaneously, by optimizing the field distribution, effective refractive index, and group refractive index characteristics of the TE and TM modes in the waveguide based on the material and dimensional parameters of this dual-core three-layer waveguide structure, the phase difference between different polarization modes during the transmission process of the arrayed waveguide grating is compensated. This allows optical signals of different polarization states to be focused at the same wavelength position at the output end, thereby reducing the polarization sensitivity of the arrayed waveguide grating structure, improving the stability and reliability of spectral splitting, and reducing center wavelength drift, channel crosstalk, and insertion loss caused by polarization.

[0023] In this embodiment or other embodiments, the input planar waveguide 2 and the output planar waveguide 4 can also adopt a vertically coupled dual-core three-layer waveguide structure to effectively reduce optical field mismatch and coupling loss caused by mode distribution differences at the interfaces of different waveguide structures. Simultaneously, the dual-core three-layer structure in the input planar waveguide 2 and the output planar waveguide 4 can further participate in the effective refractive index difference and group refractive index difference compensation for TE and TM modes, modulating the polarization-dependent phase error generated in the planar waveguide region, thereby reducing the cumulative polarization phase error in the entire arrayed waveguide grating transmission link. This achieves phase consistency control between the TE and TM modes throughout the entire propagation path of the arrayed waveguide grating structure, improving the focusing consistency of optical signals with different polarization states at the output end, further improving the polarization insensitivity performance of the AWG, and reducing polarization-dependent loss and channel crosstalk. The planar waveguide region refers to the regions of the input planar waveguide 2 and the output planar waveguide 4.

[0024] In one embodiment, in the dual-core three-layer waveguide structure, the first waveguide core layer 31 and the second waveguide core layer 33 are made of the same or different high-refractive-index waveguide materials, and their thicknesses are both any value between 200nm and 800nm. The isolation layer 32 is made of a low-refractive-index dielectric material, and its thickness is any value between 5nm and 50nm, to ensure that the dual-core three-layer waveguide structure has a suitable refractive index distribution and optical field coupling strength. The high-refractive-index waveguide materials include, but are not limited to, Si and Si3N4. The low-refractive-index dielectric materials include, but are not limited to, SiO2. The high-refractive-index first waveguide core layer 31 and second waveguide core layer 33 are used to confine the optical field propagation, and the low-refractive-index isolation layer 32 is used to adjust the coupling degree between the two core layers. By optimizing the thicknesses of the first waveguide core layer 31, second waveguide core layer 33, and isolation layer 32, it is possible to achieve TE mode and TM mode optical field distribution modulation with a smaller device size, thereby improving the polarization phase compensation effect. By defining the materials of the first waveguide core layer 31, the second waveguide core layer 33, and the isolation layer 32, the dual-core three-layer waveguide structure is compatible with commonly used integrated photonic platforms such as Si, Si3N4, and SiO2, which is beneficial for realizing highly integrated, low-loss on-chip spectral splitting devices.

[0025] In one embodiment, in the array waveguide 30, the length difference between two adjacent waveguides 3 is the same to form a fixed optical path difference, that is, the preset optical path difference between adjacent waveguides 3 is a fixed value; thereby ensuring that optical signals of different wavelengths can generate a stable phase accumulation difference after transmission through the array waveguide 30, realizing high-precision wavelength separation based on interference effect. In some embodiments, the array waveguide 30 includes at least 7 waveguides 3. The array structure composed of at least 7 waveguides 3 can ensure that the array waveguide grating structure has sufficient spectral resolution and channel separation capability. In other embodiments, each waveguide 3 is designed as a ridge-type dual-core three-layer waveguide structure or a strip-type dual-core three-layer waveguide structure, so that while realizing the functions of optical path difference accumulation and spectral separation, the array waveguide 30 region can compensate for the phase mismatch of different polarization modes during propagation in the array waveguide 30, reduce the center wavelength drift caused by polarization, and improve the polarization stability and spectral output consistency of the array waveguide grating. Meanwhile, suitable strip waveguide 3 structures can be selected according to different material platforms, processing technology and spectral resolution requirements: ridge-type dual-core three-layer waveguide structure and strip-type dual-core three-layer waveguide structure, which can improve device design flexibility and process compatibility while ensuring polarization-insensitive transmission performance.

[0026] In one embodiment, the strip waveguide 3 is preferably a ridge-type dual-core three-layer waveguide structure. For example... Figure 2 , Figure 3 As shown, in this waveguide 3, the second waveguide core layer 33 has a protruding ridge waveguide, and the height of the ridge waveguide is 0.75-0.95 times the thickness of the second waveguide core layer 33, and the width is any value between 650nm and 950nm, ensuring that the waveguide 3 has suitable mode confinement capability and optical field coupling characteristics. The isolation layer 32 and the first waveguide core layer 31 are sequentially disposed on the ridge waveguide along the thickness direction, and the widths of the first waveguide core layer 31 and the isolation layer 32 are matched with the width of the ridge waveguide. This ridge structure can reduce mode leakage and propagation loss, and improve the transmission efficiency and structural stability of the arrayed waveguide grating device. In some embodiments, the waveguide 3 is preferably a strip-shaped dual-core three-layer waveguide structure. Figure 4 , Figure 5 As shown, in this waveguide 3, the first waveguide core layer 31, the isolation layer 32 and the second waveguide core layer 33 are stacked sequentially along the thickness direction, and the widths of the three are the same, all ranging from 650nm to 950nm. This strip structure can ensure that the strip waveguide 3 can achieve polarization compensation in a small size. At the same time, it effectively reduces the processing complexity and improves the consistency of device manufacturing, making it suitable for large-scale on-chip photonic integration manufacturing.

[0027] In one embodiment, such as Figure 6As shown, the input planar waveguide 2 includes an incident arc surface and an exit arc surface; the radius of the circle corresponding to the exit arc surface is any value between 30μm and 150μm, and the ratio of the radius of the circle corresponding to the exit arc surface to the radius of the circle corresponding to the incident arc surface is any value between 1.8 and 2.2. In this embodiment or other embodiments, the output planar waveguide 4 has the same structure as the input planar waveguide 2 and is symmetrically arranged relative to the array waveguide 30. By limiting the dimensional relationship between the incident and exit arc surfaces of the input planar waveguide 2 and the output planar waveguide 4, the planar waveguide region satisfies the Rowland circle focusing condition of the array waveguide grating, improving the spatial focusing accuracy of different wavelength optical signals at the output end. By adopting a symmetrical structure for the input planar waveguide 2 and the output planar waveguide 4, the structural design complexity can be reduced, and the optical field transmission characteristics in different propagation directions can be kept consistent, which is beneficial to improving the consistency of the AWG spectral channels and reducing output spectral drift and inter-channel crosstalk. In some embodiments, the input planar waveguide 2 and the output planar waveguide 4 preferably adopt a dual-core three-layer waveguide structure.

[0028] In one embodiment, the input waveguide 1 includes at least one input strip waveguide 11. This input strip waveguide 11 is arranged along the incident arc surface of the input planar waveguide 2 and coupled to it to form a single-input-port structure or a multi-input-port structure. This allows the arrayed waveguide grating structure to be suitable for different spectral acquisition and optical path coupling requirements, improving device design flexibility and application range. Furthermore, the input strip waveguide 11 preferably adopts a dual-core three-layer waveguide structure of the same type as the strip waveguide 3, to achieve mode matching of the input optical signal between the input waveguide 1 and the arrayed waveguide 30, reducing energy loss during input coupling. In this embodiment or other embodiments, the output waveguide 5 includes multiple output strip waveguides 51, which are arranged along the exit arc surface of the output planar waveguide 4. This allows different wavelength optical signals, after being focused by the output planar waveguide 4, to enter their respective output channels, achieving high-precision spatial spectral separation and improving spectral detection resolution and channel output stability. In addition, the output strip waveguide 51 also adopts the same type of dual-core three-layer waveguide structure as the strip waveguide 3, to ensure mode continuity between the output area and the array waveguide 30 area and reduce optical signal coupling loss.

[0029] One embodiment provides a design method for the above-mentioned arrayed waveguide grating structure. The principle of this design method is as follows: taking the total phase difference between the TE and TM modes in the overall spectral transmission channel of the arrayed waveguide grating structure as the optimization object, the polarization mismatch is decomposed into a fixed polarization phase offset term near the center wavelength. And the first-order drift that accumulates with frequency, i.e., the polarization phase drift term. Based on the regions where different mismatch terms occur, the cross-sectional structures of the array waveguide 30 region and the planar waveguide region are optimized to achieve staged compensation of polarization phase error. This design method includes the following steps: S1. Based on the arrayed waveguide grating structure satisfying the Loland circular grating beam splitting principle, the optical path difference relationship between adjacent waveguides (3) is established: , In the formula, It is the effective refractive index corresponding to the TE mode or TM mode in region 30 of the arrayed waveguide. It is the length difference between adjacent waveguides 3 in the region of array waveguide 30. It is the center-to-center spacing between adjacent waveguides 3 in the region of array waveguide 30. It is the effective refractive index corresponding to the TE mode or TM mode in the planar waveguide region, which is the input planar waveguide 2 and the output planar waveguide 4 region. It is the angle between the central axis of any input strip waveguide 11 on the incident end arc surface of the input planar waveguide 2 and the central axis of the incident end arc surface. λ is the angle between the central axis of any output strip waveguide 51 on the output end arc surface of the output planar waveguide 4 and the central axis of the output end arc surface, m is the grating order of the array waveguide grating structure, and λ is the center wavelength of the incident light in vacuum. S2. Based on the optical path difference formula, establish the transmission phases corresponding to the TE mode or TM mode in the arrayed waveguide 30 region and the planar waveguide region, respectively, and establish the total transmission phases of the TE mode or TM mode in the arrayed waveguide 30 region and the planar waveguide region; wherein, a propagation constant is introduced in the arrayed waveguide 30 region. The transmission phase expression for the TE mode or TM mode in region 30 of the array waveguide is as follows: ; The transmission phase expression for the TE mode or TM mode in the planar waveguide region is: ; Since the arrayed waveguide grating structure includes a planar waveguide region and an arrayed waveguide 30 region, the overall phase of light passing through the arrayed waveguide grating structure device can be represented by the sum of the phase of the planar waveguide region and the phase of the arrayed waveguide 30 region. That is, the total transmission phase The expression is: , In the formula, is the propagation constant corresponding to the TE mode or TM mode in region 30 of the array waveguide; c is the frequency of light wave propagation; c is the speed of light in a vacuum. The deployment is carried out within the target operating band, that is, at the optical transmission frequency. By approximating the small bandwidth region, the transmission phase expressions for TE mode or TM mode in the arrayed waveguide 30 region and the planar waveguide region are obtained as follows: , , In the formula, This represents frequency variation terms of third order and above. The center frequency of the target operating band; The group refractive index corresponding to the TE mode or TM mode in the region of the array waveguide (30) is It is the group refractive index corresponding to the TE mode or TM mode in the planar waveguide region; S3. Based on the total transmission phase expression, establish a polarization phase mismatch model between the TE mode and the TM mode within the same spectral channel, and decompose it into a fixed polarization phase offset term. With polarization phase drift term ; The transmission phase difference between TE mode and TM mode The expression is: , in, , , , ; Fixed polarization phase shift term The expression is: , Polarization phase drift term The expression is: , In the formula, The effective refractive index difference between the TE and TM modes in region 30 of the arrayed waveguide. The group refractive index difference between the TE and TM modes in region 30 of the arrayed waveguide. The effective refractive index difference between the TE and TM modes in the planar waveguide region. The group refractive index difference between the TE and TM modes in the planar waveguide region; S4. Adjust the structural parameters of the strip waveguide 3 in the array waveguide 30 region, and the structural parameters of the input strip waveguide 11 and the output strip waveguide 51 in the planar waveguide region, so that the polarization phase shift term... Polarization phase drift term It also meets the preset polarization compensation conditions.

[0030] In step S1, It is the effective refractive index corresponding to the TE mode or TM mode in region 30 of the arrayed waveguide, i.e. express or Similarly, express or In step S3, express or ; express or .

[0031] In step S3, formula (7) can be transformed into: , Equation (10) characterizes the phase mismatch relationship between different polarization modes in the array waveguide region 30 and the planar waveguide region. From Equation (10), it can be seen that the phase difference between the two polarization states of light propagating in each spectral channel can be considered as the center frequency of that channel. and channel frequency This represents a linear relationship between the independent variables. Therefore, this embodiment aims to reduce the fixed polarization phase offset and polarization phase drift terms. Based on the determined center wavelength, bandwidth, and input / output structural parameters of the spectral channel, the material parameters, geometric dimensions, and vertical coupling characteristics of the dual-core three-layer waveguide structure are adjusted to ensure that the effective refractive index difference and group refractive index difference in the array waveguide 30 region and the effective refractive index difference and group refractive index difference in the planar waveguide region satisfy the polarization phase compensation relationship. This reduces the cumulative phase difference between the TE mode and the TM mode during the entire array waveguide grating transmission process.

[0032] In step S3, when the polarization phase shift term Polarization phase drift term When the preset polarization compensation conditions are met, the structural parameters of each part of the polarization-insensitive array waveguide grating structure can be obtained, and then the polarization-insensitive array waveguide grating structure can be designed and fabricated based on these structural parameters.

[0033] This embodiment establishes a transmission phase model for the TE and TM modes in an arrayed waveguide grating, decomposing the phase mismatch between different polarization modes into a fixed polarization phase offset term. and the polarization phase drift term that varies with frequency Structural parameters were optimized for both the array waveguide 30 region and the planar waveguide region to achieve phased compensation for polarization error sources. This enables the TE mode and TM mode to spatially overlap at the output channel, improving the accuracy and repeatability of polarization-insensitive AWG designs and avoiding the additional losses and complex packaging problems associated with traditional methods that rely on additional structures such as polarization rotators and polarization beam splitters.

[0034] In this embodiment or other embodiments, the preset polarization phase compensation condition includes a fixed polarization phase offset term. And polarization phase drift term By simultaneously reducing the polarization phase shift at the center frequency and the polarization phase drift during frequency changes, it is possible to effectively suppress center wavelength shift, spectral peak broadening, and channel crosstalk caused by different polarization states, thereby improving the polarization stability and spectral measurement accuracy of the arrayed waveguide grating over a wide spectral range.

[0035] Example 1 A polarization-insensitive arrayed waveguide grating structure includes an input waveguide 1, an input planar waveguide 2, an arrayed waveguide 30, an output planar waveguide 4, and an output waveguide 5, which are sequentially connected along the light propagation direction and disposed on a substrate layer 6. The arrayed waveguide 30 includes multiple strip waveguides 3, with adjacent strip waveguides 3 having the same length difference to form a fixed optical path difference. The input waveguide 1 includes an input strip waveguide 11. The output waveguide 5 includes multiple output strip waveguides 51. The input strip waveguide 11, each waveguide 3, and each output strip waveguide 51 all employ a strip-shaped dual-core three-layer waveguide structure. This strip-shaped dual-core three-layer waveguide structure includes, along the thickness direction, a first waveguide core layer 31, an isolation layer 32, and a second waveguide core layer 33. The first waveguide core layer 31 and the second waveguide core layer 33 are made of Si3N4 material, and the isolation layer 32 is made of SiO2 material. This ensures that the refractive indices of the first waveguide core layer 31 and the second waveguide core layer 33 are the same and greater than the refractive index of the isolation layer 32, thus guaranteeing a vertical dual-core optical field coupling structure between the first waveguide core layer 31 and the second waveguide core layer 33. The input planar waveguide 2 and the output planar waveguide 4 also employ a dual-core three-layer waveguide structure, and the material type and thickness parameters of the first waveguide core layer 31, the isolation layer 32, and the second waveguide core layer 33 are the same as those of the strip-shaped dual-core three-layer waveguide structure, ensuring mode continuity of the optical signal during transmission at the input, array region, and output ends. The substrate layer 6 of this array waveguide grating structure is made of SiO2 material. In this array waveguide grating structure, SiO2, the same material as the substrate layer 6, is used as a protective layer; that is, after the array waveguide grating structure is formed on the substrate layer 6, a SiO2 layer is deposited on the array waveguide grating structure.

[0036] The structural parameters of the arrayed waveguide grating structure are optimized by taking the total phase difference between the TE mode and the TM mode in the overall spectral transmission channel as the optimization object.

[0037] First, based on the principle that the arrayed waveguide grating satisfies the beam splitting principle of the Rowland circular grating, the optical path difference relationship between adjacent waveguides 3 is established: , Establish the transmission phases corresponding to TE mode or TM mode in the array waveguide 30 region and the planar waveguide region respectively, and establish the total transmission phase of TE mode or TM mode in the array waveguide 30 region and the planar waveguide region. In this context, a propagation constant is introduced in region 30 of the array waveguide. The transmission phase expression for TE mode or TM mode is: ; The transmission phase expression for the TE mode or TM mode in the planar waveguide region is: ; The expression for the total transmission phase is: ; Using light wave transmission frequency By approximating the small bandwidth region, the transmission phase expressions for TE mode or TM mode in the arrayed waveguide 30 region and the planar waveguide region are obtained as follows: , .

[0038] Next, based on the above total transmission phase expression, a polarization phase mismatch model between the TE mode and the TM mode within the same spectral channel is established, and a fixed polarization phase offset term is obtained by decomposition. and polarization phase drift term The transmission phase difference between TE mode and TM mode. The expression is: , in, , , , ; Fixed polarization phase shift term The expression is: , Polarization phase drift term The expression is: , Therefore, the phase difference between TE mode and TM mode can be expressed as: (10). As can be seen from formula (10), the phase difference between the TE mode and the TM mode in a single spectral channel is determined by the fixed polarization phase shift term at the center frequency. and the polarization phase drift term that varies with frequency A joint decision.

[0039] Subsequently, based on the aforementioned polarization phase compensation relationship, the structural parameters of the strip waveguide 3 in the array waveguide 30 region are optimized to make the fixed polarization phase offset term The preset polarization compensation conditions are met. Simultaneously, the structural parameters of the input strip waveguide 11 and the output strip waveguide 51 in the planar waveguide region are optimized to reduce the polarization phase drift term. The preset polarization compensation conditions are met.

[0040] When the polarization phase offset term is fixed Polarization phase drift term When the preset polarization compensation conditions are met, the structural parameters of the arrayed waveguide grating structure are obtained. These structural parameters include: in the strip-shaped dual-core three-layer waveguide structure, the thickness of the first waveguide core layer 31 is 400 nm, the thickness of the isolation layer 32 is 10 nm, and the thickness of the second waveguide core layer 33 is 400 nm. The widths of the first waveguide core layer 31, the isolation layer 32, and the second waveguide core layer 33 are all the same, 880 nm. Furthermore, the thicknesses of the first waveguide core layer 31, the isolation layer 32, and the second waveguide core layer 33 in the input planar waveguide 2 and the output planar waveguide 4 are the same as those in the strip-shaped dual-core three-layer waveguide structure. The radius of the circle corresponding to the arc surface at the exit end of the input planar waveguide 2 is 41.2 μm, which is twice the radius of the circle corresponding to the arc surface at its incident end. The radius of the circle corresponding to the arc surface at the incident end of the output planar waveguide 4 is 41.2 μm, which is twice the radius of the circle corresponding to the arc surface at its exit end. Based on these structural parameters, a polarization-insensitive arrayed waveguide grating structure was designed and fabricated.

[0041] The spectral output performance of the fabricated arrayed waveguide grating structure was tested, and the test results are as follows: Figure 7 As shown.

[0042] Depend on Figure 7It can be seen that the arrayed waveguide grating structure fabricated in this embodiment achieves polarization-insensitive spectral output over a wide spectral range. This structure has nine spatially separated spectral output channels (corresponding to the number of output strip waveguides 51), with an adjacent channel spacing of 2.74 nm, a spectral half-maximum bandwidth of 1.93 nm, and covers a spectral range of 1638 nm to 1664.8 nm. Simultaneously, within the same output channel, the maximum center wavelength drift corresponding to the TE and TM polarization states is 0.165 nm, the maximum polarization-dependent loss is 0.21 dB, the maximum channel crosstalk is -16.34 dB, and the output spectral non-uniformity is 1.44 dB. These results demonstrate that this embodiment, through a dual-core, three-layer waveguide structure, compensates for the effective refractive index difference and group refractive index difference between the TE and TM modes, enabling wavelength focusing of optical signals with different polarization states at the same output channel position. This effectively reduces the polarization sensitivity of the arrayed waveguide grating structure and improves the output stability of the on-chip spectral splitter.

[0043] Example 2 The difference between this embodiment and Embodiment 1 is that the input strip waveguide 11, each waveguide 3, and each output strip waveguide 51 all adopt a ridge-type dual-core three-layer waveguide structure. This ridge-type dual-core three-layer waveguide structure includes, along its thickness direction, a first waveguide core layer 31, an isolation layer 32, and a second waveguide core layer 33. The first and second waveguide core layers 31 and 33 are made of Si3N4 material, and the isolation layer 32 is made of SiO2 material. This ensures that the refractive indices of the first and second waveguide core layers 31 are the same and greater than the refractive index of the isolation layer 32, thus guaranteeing a vertical dual-core optical field coupling structure between the first and second waveguide core layers 31 and 33. A protruding ridge waveguide is provided on the second waveguide core layer 33. The isolation layer 32 and the first waveguide core layer 31 are sequentially stacked on the ridge waveguide along the thickness direction, so that the first waveguide core layer 31, the isolation layer 32, and the ridge-type second waveguide core layer 33 together constitute a vertical dual-core coupled waveguide structure. The input planar waveguide 2 and the output planar waveguide 4 also adopt a dual-core three-layer waveguide structure, and the material and thickness parameters of their first waveguide core layer 31, isolation layer 32 and second waveguide core layer 33 correspond to the ridge-type dual-core three-layer waveguide structure in the array waveguide 30, so as to ensure the mode continuity of the optical signal during the transmission process in the input region, array region and output region.

[0044] Using the same polarization phase compensation design method as in Example 1, a fixed polarization phase offset term between the TE mode and the TM mode is employed. and polarization phase drift term Simultaneously satisfying the polarization compensation condition as the optimization objective, the structural parameters of the ridge-type dual-core three-layer waveguide structure were optimized, resulting in the following structural parameters: In the ridge-type dual-core three-layer waveguide structure, the thickness of the first waveguide core layer 31 is 260 nm, and the thickness of the isolation layer 32 is 16 nm. The second waveguide core layer 33 includes a ridge base and a ridge waveguide disposed on the ridge base. The thickness of the ridge base is 110 nm, and the height of the ridge waveguide is 530 nm, making the total thickness of the second waveguide core layer 33 640 nm. The width of the ridge waveguide is 775 nm, and the widths of the first waveguide core layer 31 and the isolation layer 32 are the same as the width of the ridge waveguide. The thicknesses and widths of the first waveguide core layer 31, the isolation layer 32, and the second waveguide core layer 33 in the input planar waveguide 2 and the output planar waveguide 4 are the same as those in the ridge-type dual-core three-layer waveguide structure. The radius of the circle corresponding to the arc surface at the output end of the input planar waveguide 2 is 97.4 μm, which is twice the radius of the circle corresponding to the arc surface at its input end. The radius of the circle corresponding to the incident arc surface of the output planar waveguide 4 is 97.4 μm, which is twice the radius of the circle corresponding to the exit arc surface. Based on the above optimized structural parameters, a polarization-insensitive array waveguide grating structure is designed and constructed. In this embodiment, the array waveguide 30 includes multiple strip waveguides 3. The ridge bottom in the second waveguide core layer 33 of each strip waveguide 3 can be a whole, that is, multiple strip waveguides 3 share the same continuous ridge bottom, and the size of the ridge bottom in the planar direction can match the size of the substrate layer 6 and the protective layer of the array waveguide grating structure; by forming multiple spaced ridge waveguides on the ridge bottom, multiple ridge-type strip waveguide 3 structures are constructed. In some other embodiments, the ridge bottom in the second waveguide core layer 33 corresponding to the multiple strip waveguides 3 can also adopt a discrete setting structure, that is, each strip waveguide 3 has an independent ridge bottom structure; the width of the ridge bottom in the lateral direction is greater than the width of the ridge waveguide set on it, so as to enhance the mode confinement capability of the ridge-type waveguide region and ensure the stable transmission of the optical field in the ridge waveguide.

[0045] The spectral output performance of the fabricated arrayed waveguide grating structure was tested, and the test results are as follows: Figure 8 As shown.

[0046] Depend on Figure 8It can be seen that the arrayed waveguide grating structure constructed in this embodiment can also achieve high-resolution polarization-insensitive spectral output within a narrow spectral range. This structure includes seven spatially separated spectral output channels, corresponding to the number of output strip waveguides 51, with an adjacent channel spectral spacing of 0.12 nm and a spectral half-width of 0.07 nm. Simultaneously, within the same output channel, the maximum center wavelength drift between the TE and TM polarization states is only 0.016 nm, the maximum polarization correlation loss is 0.17 dB, the maximum channel crosstalk is -15.23 dB, and the output spectral non-uniformity is 0.31 dB. These results demonstrate that this embodiment, by employing a ridge-type dual-core three-layer waveguide structure, significantly improves the waveguide mode constraint capability while maintaining the dual-core vertical coupling polarization compensation mechanism. This ensures that the TE and TM modes maintain highly consistent propagation characteristics during high-resolution narrowband spectral transmission, effectively reducing polarization-induced center wavelength drift and spectral channel non-uniformity, thus obtaining a polarization-insensitive arrayed waveguide grating structure suitable for high-resolution on-chip spectral dispersive systems.

[0047] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0048] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this invention patent should be determined by the appended claims.

Claims

1. A polarization-insensitive arrayed waveguide grating structure, characterized in that, It includes an input waveguide (1), an input planar waveguide (2), an array waveguide (30), an output planar waveguide (4), and an output waveguide (5) connected sequentially along the light propagation direction. The array waveguide (30) includes multiple strip waveguides (3), and there is a preset optical path difference between adjacent strip waveguides (3); The input waveguide (1), each of the waveguides (3) and the output waveguide (5) all adopt a vertically coupled dual-core three-layer waveguide structure. The dual-core three-layer waveguide structure includes, along the thickness direction, a first waveguide core layer (31), an isolation layer (32), and a second waveguide core layer (33). The refractive indices of the first waveguide core layer (31) and the second waveguide core layer (33) are both greater than the refractive index of the isolation layer (32), so that a vertical dual-core optical field coupling structure is formed between the first waveguide core layer (31) and the second waveguide core layer (33). The first waveguide core layer (31), the isolation layer (32), and the second waveguide core layer (33) have preset refractive indices and size parameters, so that the effective refractive index difference and group refractive index difference of the TE mode or TM mode during the propagation process of the array waveguide grating structure meet the polarization phase compensation condition, thereby achieving polarization-insensitive spectral separation.

2. The arrayed waveguide grating structure as described in claim 1, characterized in that, In the dual-core three-layer waveguide structure, the first waveguide core layer (31) and the second waveguide core layer (33) are made of high refractive index waveguide material and the thickness is any value between 200nm and 800nm. The isolation layer (32) is made of low refractive index dielectric material and the thickness is any value between 5nm and 50nm. The high-refractive-index waveguide material includes at least one of Si and Si3N4; the low-refractive-index dielectric material includes SiO2.

3. The arrayed waveguide grating structure as described in claim 2, characterized in that, Each of the waveguides (3) is designed as a ridge-type double-core three-layer waveguide structure or a strip-type double-core three-layer waveguide structure, and the length difference between two adjacent waveguides (3) is the same to form a fixed optical path difference.

4. The arrayed waveguide grating structure as described in claim 3, characterized in that, The waveguide (3) is a ridge-type double-core three-layer waveguide structure; In the waveguide (3), the second waveguide core layer (33) has a protruding ridge waveguide. The height of the ridge waveguide is 0.75-0.95 times the thickness of the second waveguide core layer (33), and the width is any value between 650nm and 950nm. The isolation layer (32) and the first waveguide core layer (31) are sequentially disposed on the ridge waveguide along the thickness direction, and the widths of the first waveguide core layer (31) and the isolation layer (32) are matched with the width of the ridge waveguide.

5. The arrayed waveguide grating structure as described in claim 3, characterized in that, The strip waveguide (3) is designed as a strip-shaped double-core three-layer waveguide structure; In the waveguide (3), the first waveguide core layer (31), the isolation layer (32) and the second waveguide core layer (33) are stacked sequentially along the thickness direction, and the widths of the three are the same, which are any values ​​from 650nm to 950nm.

6. The arrayed waveguide grating structure as described in claim 1, characterized in that, The input planar waveguide (2) includes an incident arc surface and an exit arc surface; the radius of the circle corresponding to the exit arc surface is any value between 30μm and 150μm, and the ratio of the radius of the circle corresponding to the exit arc surface to the radius of the circle corresponding to the incident arc surface is any value between 1.8 and 2.

2. The output planar waveguide (4) has the same structure as the input planar waveguide (2) and is symmetrically arranged relative to the array waveguide (30).

7. The arrayed waveguide grating structure as described in claim 6, characterized in that, The input planar waveguide (2) and the output planar waveguide (4) adopt a dual-core three-layer waveguide structure.

8. The arrayed waveguide grating structure as described in claim 1, characterized in that, The input waveguide (1) includes at least one input strip waveguide (11), and the input strip waveguide (11) adopts the same type of dual-core three-layer waveguide structure as the strip waveguide (3) to achieve mode matching of the input optical signal between the input waveguide (1) and the array waveguide (30); The output waveguide (5) includes multiple output strip waveguides (51), and the output strip waveguides (51) adopt the same type of dual-core three-layer waveguide structure as the strip waveguide (3); Multiple output strip waveguides (51) are arranged along the arc direction of the output flat waveguide (4) to couple out different wavelength optical signals after being focused by the output flat waveguide (4).

9. The design method of the arrayed waveguide grating structure according to any one of claims 1-8, characterized in that, Includes the following steps: S1. Based on the arrayed waveguide grating structure satisfying the Loland circular grating beam splitting principle, the optical path difference relationship between adjacent waveguides (3) is established: , In the formula, It is the effective refractive index corresponding to the TE mode or TM mode in the region of the arrayed waveguide (30). It is the length difference between adjacent waveguides (3) in the region of the array waveguide (30). It is the center-to-center spacing between adjacent waveguides (3) in the region of the array waveguide (30). It is the effective refractive index corresponding to the TE mode or TM mode in the planar waveguide region, where the planar waveguide region is the region of the input planar waveguide (2) and the output planar waveguide (4). It is the angle between the central axis of any input strip waveguide (11) on the incident end arc surface of the input planar waveguide (2) and the central axis of the incident end arc surface. is the angle between the central axis of any output strip waveguide (51) on the arc surface of the output flat waveguide (4) and the central axis of the arc surface of the output end, m is the grating order of the array waveguide grating structure, and λ is the center wavelength of the incident light. S2. Based on the optical path difference relationship, establish the transmission phases corresponding to the TE mode or TM mode in the arrayed waveguide (30) region and the planar waveguide region, respectively, and establish the total transmission phase of the TE mode or TM mode in the arrayed waveguide (30) region and the planar waveguide region. The expression is: ， In the formula, The propagation constant corresponding to the TE mode or TM mode in the region of the array waveguide (30); c is the frequency of the optical signal; c is the speed of light in a vacuum. The transmission phase corresponding to the TE mode or TM mode in the region of the array waveguide (30) The transmission phase corresponding to the TE mode or TM mode in the planar waveguide region; The propagation phase expressions for the TE mode or TM mode in the array waveguide (30) region and the planar waveguide region are obtained by unfolding within the target operating band: ， ， In the formula, This represents frequency variation terms of third order and above. The center frequency of the target operating band; The group refractive index corresponding to the TE mode or TM mode in the region of the array waveguide (30) is It is the group refractive index corresponding to the TE mode or TM mode in the planar waveguide region; S3. Based on the expression for the total transmission phase, establish a polarization phase mismatch model between the TE mode and the TM mode within the same spectral channel, and decompose it into a fixed polarization phase offset term. With polarization phase drift term ; The transmission phase difference between TE mode and TM mode The expression is: ， The fixed polarization phase offset term The expression is: ， The polarization phase drift term The expression is: ， In the formula, The effective refractive index difference between the TE mode and the TM mode in the region of the array waveguide (30) is given. The group refractive index difference between the TE mode and the TM mode in the region of the array waveguide (30) is given. The effective refractive index difference between the TE mode and the TM mode in the planar waveguide region is given. The group refractive index difference between the TE mode and the TM mode in the planar waveguide region; S4. Adjust the structural parameters of the strip waveguide (3) in the array waveguide (30) region, the input strip waveguide (11) and the output strip waveguide (51) in the planar waveguide region, so that the polarization phase shift term Polarization phase drift term It also meets the preset polarization compensation conditions.

10. The design method as described in claim 9, characterized in that, The preset polarization phase compensation condition includes a fixed polarization phase offset term. And polarization phase drift term .

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