An on-chip polarization-insensitive detector system

Abstract

This invention discloses an on-chip polarization-insensitive detector system. The system splits arbitrary polarized light into two branches for output (TE and TM modes), and these two branches are then output to both ends of the detector; the output power of the two branches is equal. The system includes an edge coupler, a waveguide interlayer coupler, an on-chip PRBS device, a 1-to-2 optical power splitter, and a detector. This invention's polarization-splitting, wave-splitting, and wave-combining method ensures that any input polarization state can be supplied with almost constant and identical optical power to both ends of the detector, mitigating the large-scale carrier shielding effect while maintaining polarization insensitivity. The incident polarization rotation beamsplitter and the wave-combining polarization beamsplitter use a mirror-image configuration to compensate for the time delays of the TE and TM modes, ensuring low polarization-dependent delays throughout the entire link when the polarization state changes.

Description

Technical Field

[0001] This invention relates to an on-chip polarization-insensitive detector system, specifically to a polarization-insensitive detector integrated on a silicon-based optical chip. Background Technology

[0002] On-chip detectors offer advantages such as small size, high integration, and balanced responsivity and bandwidth performance, making them widely used in transceiver components and modules for optical communication and optical connectivity. Germanium-silicon (GeSi) detectors can operate in both the O-band and C-band communication bands, and their processes are compatible with CMOS lines, enabling mass production. They are now integrated into the processes of almost all silicon photonics foundries.

[0003] Currently, short-range connections for applications such as data centers and optical computing primarily employ intensity modulation reception. At the receiving end, the polarization state of the incident light signal varies randomly. Furthermore, the intensity of the incident light signal at the receiving end is also random. When the incident light power is high, a significant carrier shielding effect occurs in the detector, causing a decrease in the device's bandwidth performance. To address or mitigate these two issues, a polarization beam splitter (PRBS) is typically used at the incident end to separate the transverse electric (TE) and transverse magnetic (TM) modes of the incident light signal and convert them into two TE modes, which are then incident on both ends of the on-chip detector. Double-ended incident light reduces carrier shielding effects under high light intensity compared to single-ended incident light. However, because the polarization of the incident light is random, the ratio of the two optical fields output from the PRBS also varies randomly. This randomness causes variations in the intensity of the incident light at one end of the detector. In one case, the incident light polarization is in pure TE and TM modes, and the light is incident on the detector from the single end. In another case, the TE and TM components of the incident light polarization are the same, and the incident light is incident on the detector from both ends with the same incident components. This polarization dependence of the incident light causes randomness in the strength of the carrier shielding effect, affecting the device performance. Summary of the Invention

[0004] The purpose of this invention is to propose an on-chip polarization-insensitive detector system, and the technical solution adopted is as follows:

[0005] An on-chip polarization-insensitive detector system, wherein the system splits the TE mode and TM mode of arbitrary polarized light into two branches for output, and the two branches are then output to both ends of the detector; the output power of the two branches is equal.

[0006] A further preferred embodiment of the technical solution of the present invention includes an edge coupler, a waveguide interlayer coupler, an on-chip PRBS device, a 1-to-2 optical power splitter, and a detector. The edge coupler transmits the optical signal in the external optical fiber into the chip. The waveguide interlayer coupler couples the light from the edge coupler into the silicon waveguide. The output end of the waveguide interlayer coupler is connected to the input end of the on-chip PRBS device. The on-chip PRBS device splits the input mixed polarization state into two outputs: TE mode and TM mode, and converts the TM mode into the on-chip TE mode. The two outputs are respectively connected to the input end of the 1-to-2 optical power splitter for beam splitting, and the output optical paths of the 1-to-2 optical power splitter are crossed in pairs and combined by a polarization rotation beam splitter and incident on both ends of the detector.

[0007] In a further preferred embodiment of the technical solution of the present invention, the on-chip PRBS device is a polarization rotating beam splitter, which includes a polarization rotating beam splitter for incident light splitting, a polarization rotating beam splitter I for beam combining, and a polarization rotating beam splitter II for beam combining.

[0008] In a further preferred embodiment of the technical solution of the present invention, the edge coupler is made of silicon nitride material.

[0009] In a further preferred embodiment of the technical solution of the present invention, the output of the one-to-two optical power splitter is connected to the detector via a waveguide.

[0010] In a further preferred embodiment of the technical solution of the present invention, the system includes an edge coupler, a silicon nitride one-to-two optical power splitter, a waveguide interlayer coupler, and a detector. The edge coupler transmits the optical signal in the external optical fiber into the chip. The silicon nitride one-to-two optical power splitter splits the incident optical signal into two output branches, each of which includes TE and TM modes. Both output branches are transmitted to both ends of the detector through a second waveguide, a waveguide interlayer coupler, and a third waveguide.

[0011] In a further preferred embodiment of the technical solution of the present invention, the edge coupler and the silicon nitride one-to-two optical power splitter are connected by a silicon nitride waveguide.

[0012] In a further preferred embodiment of the technical solution of the present invention, the second waveguide is a silicon nitride waveguide and the third waveguide is a silicon waveguide.

[0013] In a further preferred embodiment of the technical solution of the present invention, the second waveguide and the third waveguide have different structures and lengths.

[0014] The advantages of this invention compared to the prior art are as follows:

[0015] The on-chip polarization-insensitive detector of this invention uses an on-chip incident polarization rotating beamsplitter to split the TE and TM modes of the incident chip optical signal into two outputs, and converts the TM mode into an on-chip TE mode. Subsequent transmission optical paths use the same mode, ensuring optical path consistency, simplifying the device, and guaranteeing low PDL and latency of the link. The two outputs of the on-chip incident polarization rotating beamsplitter are respectively connected to the input of a 1-to-2 optical power equalizer for beam splitting, and the output optical paths of the optical power equalizer are crossed in pairs and combined by the polarization rotating beamsplitter and incident on both ends of the detector. This polarization splitting, beam splitting, and beam combining method ensures that the optical power input to both ends of the detector is almost constant and the same when any polarization state is input, reducing the large-scale carrier shielding effect while maintaining polarization insensitivity. The incident polarization rotating beamsplitter and the beam combining polarization beamsplitter use a mirror form to compensate for the latency of the TE and TM modes, ensuring low polarization-dependent latency of the entire link when the polarization state changes.

[0016] The on-chip polarization-insensitive detector of this invention uses an on-chip 1-to-2 power splitter to split the incident optical signal into two output paths with low loss and low polarization delay (PDL). Each path includes both TE and TM modes, and the two subsequent transmission branches are identical, ensuring optical path consistency, simplifying the device, and guaranteeing a low PDL. Each branch can simultaneously transmit both TE and TM modes. Each branch contains two waveguide structures, and the two waveguides transfer the optical signal through an interlayer coupler. For TE and TM modes, the time delay difference between the two waveguide structures is exactly opposite. By appropriately selecting the lengths of the two waveguides, low PDL and low polarization delay are achieved. This method of simultaneously splitting the signal into two branches and transmitting TE and TM modes, using two waveguide structures to compensate for the polarization delay difference, ensures that the optical power input to both ends of the detector is almost constant and the same regardless of the polarization state input, thus reducing the shielding effect of large-scale carriers while maintaining polarization insensitivity. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of the on-chip polarization insensitive detector system of Example 1;

[0018] Figure 2 This is the coupling loss curve between the edge coupler and the single-mode fiber in Example 1;

[0019] Figure 3 These are the loss curves of the waveguide interlayer coupler in Example 1 for different polarization states;

[0020] Figure 4 This is the loss curve of the on-chip PRBS in Example 1;

[0021] Figure 5 These are the intrinsic responsivity curves of the germanium-silicon detector in Example 1 under different input states;

[0022] Figure 6 This is a schematic diagram of the on-chip polarization-insensitive detector system of Example 2;

[0023] Figure 7 This is the loss curve of the silicon nitride one-to-two optical power divider implemented by a 1x2 multimode interference coupler in Example 2;

[0024] Figure 8 These are the group refractive index curves of the third and second waveguides in Example 2;

[0025] Wherein, 1-edge coupler, 2-waveguide interlayer coupler, 3-detector;

[0026] 101 - On-chip PRBS device; 101a - Polarization rotating beamsplitter for incident beam splitting; 101b - Polarization rotating beamsplitter I for beam combining; 101c - Polarization rotating beamsplitter II for beam combining; 102 - One-to-two optical power splitter; 102a - One-to-two optical power splitter I; 102b - One-to-two optical power splitter II; 103a - Waveguide I; 104a - Waveguide II; 103b - Waveguide III; 104b - Waveguide IV.

[0027] 601 - First silicon nitride waveguide, 602 - Silicon nitride one-to-two optical power splitter, 603 - Second waveguide, 603a - Silicon nitride waveguide I, 603b - Silicon nitride waveguide II, 604 - Third waveguide, 604a - Silicon waveguide III, 604b - Silicon waveguide IV, 2a - Waveguide interlayer coupler I, 2b - Waveguide interlayer coupler II. Detailed Implementation

[0028] To make the objectives, technical solutions, and advantages of this invention clearer, the following description is provided in conjunction with the appendix. Figures 1-8 The present invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention. Furthermore, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0029] Example 1

[0030] like Figure 1As shown, this embodiment proposes an on-chip polarization-insensitive detector system, including an edge coupler 1, a waveguide interlayer coupler 2, a polarization rotating beamsplitter 101a for incident light splitting, two-way optical power splitters 102 (one-way optical power splitter I 102a and one-way optical power splitter II 102b), transmission waveguides 104a and 104b, two-way polarization rotating beamsplitters (one-way polarization rotating beamsplitter I 101b and one-way polarization rotating beamsplitter II 101c) for wave combining, and a detector 3. In this embodiment, the final two outputs are sent to the detector 3. To achieve polarization insensitivity, the superposition loss and responsivity of all devices in this embodiment 1 need to meet the requirement of low polarization sensitivity.

[0031] like Figure 2 As shown, edge coupler 1 has low loss and low polarization-dependent (PDL) characteristics. In this embodiment, edge coupler 1 is made of silicon nitride material, such as... Figure 2 As shown in the figure, the coupling loss curve between the edge coupler 1 and the single-mode fiber in this embodiment 1 shows that the single-end loss is <0.8dB and the PDL is <0.3dB.

[0032] Waveguide interlayer coupler 2 is used to couple light from the silicon nitride waveguide to the silicon waveguide, specifically by coupling light from the edge coupler 1 into the on-chip PRBS device 101. Figure 3 As shown in the figure, in this embodiment 1, the loss curves of the waveguide interlayer coupler 2 for different polarization states show that the loss is <0.25dB and the PDL is <0.1dB.

[0033] The on-chip PRBS device (polarization rotating beam splitter) 101 is made of silicon. The polarization rotating beam splitter includes an incident beam splitter 101a, a beam combining polarization rotating beam splitter I 101b, and a beam combining polarization rotating beam splitter II 101c. For example... Figure 4 As shown in the figure, in this embodiment 1, the loss curves of the on-chip PRBS device 101 for different input polarization states show that the TE mode has almost no loss and PDL < 0.3dB.

[0034] like Figure 1 As shown, the input beam splitter 101a is connected to the output of the waveguide interlayer coupler 2 to split the input mixed polarization state into two outputs. The input TE mode optical signal is output from the upper branch and connected to the input of the 1-to-2 optical power splitter I 102a. The input TM mode optical signal is converted to TE mode and output from the lower branch, connected to the input of the 1-to-2 optical power splitter II 102b.

[0035] In this embodiment 1, the one-to-two optical power splitter 102 is a silicon waveguide one-to-two optical power splitter, which can preferably be implemented by a 1x2 multimode interference coupler, a directional coupler, a thermally adiabatic directional coupler, etc.

[0036] One output of the 1-to-2 optical power splitter I 102a is connected to waveguide I 103a, and the other output is connected to waveguide II 104a; one output of the 1-to-2 optical power splitter II 102b is connected to waveguide III 103b, and the other output is connected to waveguide IV 104b; waveguide I 103a, waveguide II 104a, waveguide III 103b and waveguide IV 104b are all silicon waveguides, and their materials, structures and lengths are all the same.

[0037] like Figure 1 As shown, the on-chip PRBS device 101 in this embodiment is a polarization rotating beamsplitter, including one polarization rotating beamsplitter 101a for incident light splitting and two polarization rotating beamsplitters for beam combining, namely, polarization rotating beamsplitter I 101b and polarization rotating beamsplitter II 101c for beam combining. The structures of polarization rotating beamsplitter I 101b and polarization rotating beamsplitter II 101c for beam combining are the same as those of polarization rotating beamsplitter 101a for incident light splitting, and the directions of polarization rotating beamsplitter I 101b and polarization rotating beamsplitter II 101c for beam combining are mirror images of polarization rotating beamsplitter 101a for incident light splitting.

[0038] One end of the polarization rotating beamsplitter I 101b is connected to one end of waveguide II 104a, and the other end of the polarization rotating beamsplitter I 101b is connected to one end of waveguide IV 104b. The signal is combined by the polarization rotating beamsplitter I 101b into a mixed TE and TM mode input to one end of the detector 3. Since the polarization rotating beamsplitter I 101b is a mirror image of the incident light polarization rotating beamsplitter 101a, the polarization correlation loss and polarization correlation delay introduced by the incident light polarization rotating beamsplitter 101a are compensated by the polarization rotating beamsplitter I 101b.

[0039] One end of the polarization rotating beamsplitter II 101c for wave combining is connected to one end of waveguide I 103a, and the other end of the polarization rotating beamsplitter II 101c for wave combining is connected to one end of waveguide III 103b. The signal is combined by the polarization rotating beamsplitter II 101c for wave combining into a mixed TE and TM mode and input to the other end of the detector 3. Since the polarization rotating beamsplitter II 101c for wave combining is a mirror image of the polarization rotating beamsplitter 101a for incident light splitting, the polarization correlation loss and polarization correlation delay introduced by the polarization rotating beamsplitter 101a for incident light splitting are compensated by the polarization rotating beamsplitter II 101c for wave combining.

[0040] like Figure 1As shown, detector 3 can be implemented using GeSi (germanium-silicon material) or 350-500 material. In this embodiment, a germanium-silicon detector is used. The intrinsic responsivity curves of the germanium-silicon detector under different input states are shown below. Figure 5 As shown, the responsivity across the entire band is >0.75 A / W, and the difference between TE and TM modes is <0.1 dB.

[0041] In this embodiment, the combination of all the above devices enables that, under any polarization state input, the two ends of the detector 3 can be input with almost constant and the same optical power. The PDL of the entire optical link is only introduced by the edge coupler 1 and the waveguide interlayer coupler 2, which can achieve PDL < 0.5dB, thereby reducing the large optical carrier shielding effect while maintaining the polarization insensitive characteristics.

[0042] In this embodiment, the on-chip polarization-insensitive detector system uses a polarization rotating beamsplitter 101a to split the TE and TM modes of the incident chip optical signal into two outputs, and converts the TM mode into an on-chip TE mode. Subsequent transmission optical paths use the same method to ensure optical path consistency, simplify components, and guarantee low PDL and latency of the link. The two outputs of the polarization rotating beamsplitter 101a are respectively connected to the input of a 1-to-2 optical power splitter 102 for beam splitting, and the output optical paths of the 1-to-2 optical power splitter 102 are crossed and combined by the polarization rotating beamsplitter to be incident on both ends of the detector 3. This polarization splitting and combining method ensures that the optical power input to both ends of the detector is almost constant and the same when any polarization state is input, reducing the large-scale carrier shielding effect while maintaining polarization insensitivity. The incident polarization rotating beamsplitter and the combining polarization beamsplitter use a mirror form to compensate for the latency of the TE and TM modes, ensuring low polarization-dependent latency of the entire link when the polarization state changes.

[0043] Example 2

[0044] like Figure 6 As shown, this embodiment proposes an on-chip polarization-insensitive detector system, including an edge coupler 1, a first silicon nitride waveguide 601, a silicon nitride one-to-two optical power splitter 602, a waveguide interlayer coupler 2 (including waveguide interlayer coupler I 2a and waveguide interlayer coupler II 2b), a second waveguide 603 which is a silicon nitride waveguide (including silicon nitride waveguide I 603a and silicon nitride waveguide II 603b), a third waveguide 604 which is a silicon waveguide (including silicon waveguide III 604a and silicon waveguide IV 604b), and a detector 3.

[0045] like Figure 2 As shown, edge coupler 1 has low loss and low polarization-dependent (PDL) characteristics. In this embodiment, edge coupler 1 is made of silicon nitride material, such as... Figure 2As shown in the figure, the coupling loss curve between the edge coupler 1 and the single-mode fiber in this embodiment 2 shows that the single-end loss is <0.8dB and the PDL is <0.3dB.

[0046] The first silicon nitride waveguide 601 can simultaneously transmit TE and TM modes. One end of the first silicon nitride waveguide 601 is connected to the edge coupler 1, and the other end is connected to the silicon nitride one-to-two optical power splitter 602. In this embodiment, the silicon nitride one-to-two optical power splitter 602 can be implemented using a 1x2 multimode interference coupler, a directional coupler, a thermally adiabatic directional coupler, etc. In this embodiment, the silicon nitride one-to-two optical power splitter 602 is preferably implemented using a 1x2 multimode interference coupler, such as... Figure 7 The figure shows the loss curve of the silicon nitride one-to-two optical power divider 602 implemented by a 1x2 multimode interference coupler in Embodiment 2. It can be seen that the losses of TE and TM are almost the same throughout the entire band, with PDL < 0.1dB.

[0047] like Figure 6 As shown, silicon nitride waveguide I 603a transmits both TE and TM modes simultaneously. One end of silicon nitride waveguide I 603a is connected to one output of silicon nitride 1-to-2 optical power splitter 602, and the other end is connected to the input of waveguide interlayer coupler I 2a. Silicon nitride waveguide II 603b transmits both TE and TM modes simultaneously. One end of silicon nitride waveguide II 603b is connected to the other output of silicon nitride 1-to-2 optical power splitter 602, and the other end is connected to the input of waveguide interlayer coupler II 2b.

[0048] Silicon nitride waveguide I 603a and silicon nitride waveguide II 603b are made of the same material, have the same structure, and are the same length. Waveguide interlayer couplers I 2a and II 2b couple the input light from the silicon nitride waveguide to the silicon waveguide. One end of waveguide interlayer coupler I 2a is connected to silicon nitride waveguide I 603a, and the other end is connected to one end of silicon waveguide III 604a; one end of waveguide interlayer coupler II 2b is connected to silicon nitride waveguide II 603b, and the other end is connected to one end of silicon waveguide IV 604b.

[0049] Waveguide interlayer coupler I 2a and waveguide interlayer coupler II 2b are made of the same material, have the same structure and length; silicon waveguide III 604a and silicon waveguide IV 604b are both made of silicon and can transmit TE and TM modes simultaneously.

[0050] One end of silicon waveguide III 604a is connected to waveguide interlayer coupler I 2a, and the other end is connected to one end of detector 3. One end of silicon waveguide IV 604b is connected to waveguide interlayer coupler II 2b, and the other end is connected to the other end of detector 3. Silicon waveguide III 604a and silicon waveguide IV 604b have the same material, structure and length.

[0051] Detector 3 can be implemented using GeSi (germanium-silicon material) or 350-500 material. In this embodiment, a germanium-silicon detector is used. The intrinsic responsivity curves of the germanium-silicon detector under different input states are shown below. Figure 5 As shown, the responsivity across the entire band is >0.75 A / W, and the difference between TE and TM modes is <0.1 dB.

[0052] In this embodiment, the combination of all the above-mentioned devices ensures that, regardless of the polarization state input, the optical power input to both ends of detector 3 can be almost constant and the same. The PDL of the entire optical link can be achieved as PDL < 0.5 dB, thereby reducing the large-downward carrier shielding effect while maintaining polarization insensitivity. Furthermore, in this embodiment, the group refractive index of the TE mode of the third waveguide 604 (including silicon waveguide III 604a and silicon waveguide IV 604b) is less than that of the TM mode. The group refractive index of the TE mode of the second waveguide 603 (including silicon nitride waveguide I 603a and silicon nitride waveguide II 603b) and the first silicon nitride waveguide 601 is greater than that of the TM mode. The group refractive index curves of the third waveguide 604 and the second waveguide 603 are shown below. Figure 8 As shown, this characteristic allows for the selection of a suitable length ratio between silicon waveguides and silicon nitride waveguides to compensate for the time delay of TE and TM modes caused by different waveguide structures.

[0053] In this embodiment, the time delay differences between the TE mode and TM mode introduced by the edge coupler 1, the first silicon nitride waveguide 601, the silicon nitride one-to-two optical power splitter 602, the second waveguide 603, the waveguide interlayer coupler 2, and the third waveguide 604 are set to t1~t6 respectively. By selecting an appropriate waveguide length, the total time delay difference t1+t2+t3+t4+t5+t6 of different polarizations of the center wavelength can be reduced to 0ps. Considering the entire band, the total time delay can be reduced to <0.1ps, which has almost no impact on high-speed applications of 100Gbaud or even 200Gbaud.

[0054] In this embodiment, the on-chip polarization-insensitive detector system uses a silicon nitride (SiN) one-to-two optical power splitter (602) to split the incident optical signal into two outputs with low loss and low PDL. Each output includes both TE and TM modes. The two subsequent transmission branches are identical, ensuring optical path consistency, simplifying the device, and guaranteeing a low PDL. Each branch can simultaneously transmit both TE and TM modes. Each branch contains two waveguide structures (second waveguide 603 and third waveguide 604). The second waveguide 603 and third waveguide 604 are made of different materials: silicon nitride and silicon, respectively. Their structures and lengths are also different to complement each other and achieve a low polarization delay. Figure 8As shown, the second waveguide 603 and the third waveguide 604 have opposite relative group refractive indices for the TE and TM modes, which, when combined, achieves low polarization delay. The two waveguides transfer optical signals through waveguide couplers 2 (waveguide coupler I 2a and waveguide coupler II 2b). For the TE and TM modes, the delay differences between the two waveguide structures are exactly opposite. By appropriately selecting the lengths of the two waveguides, low PDL and low polarization delay are achieved. This method of simultaneously splitting the signal into two branches and transmitting both TE and TM modes, using two waveguide structures to compensate for the polarization delay difference, ensures that for any polarization state input, the optical power input to both ends of the detector is almost constant and identical, mitigating the large-scale carrier shielding effect while maintaining polarization insensitivity.

[0055] Both Examples 1 and 2 are detector structures with light entering from both ends. Without loss of generality, the ideas of the two examples above can be used to realize detector structures with light entering from four or more ends.

[0056] Those skilled in the art will readily understand that the above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A polarisation-insensitive on-chip detector system, characterised in that, The system splits the TE mode and TM mode of arbitrary polarized light into two branches for output, and the two branches are then output to both ends of the detector; the power of the two branches is equal.

2. The on-chip polarization-insensitive detector system of claim 1, wherein, The system includes an edge coupler, a waveguide interlayer coupler, an on-chip PRBS device, a 1-to-2 optical power splitter, and a detector. The edge coupler transmits the optical signal from the external optical fiber into the chip. The waveguide interlayer coupler couples the light from the edge coupler into the silicon waveguide. The output of the waveguide interlayer coupler is connected to the input of the on-chip PRBS device. The on-chip PRBS device splits the input mixed polarization state into two outputs, TE mode and TM mode, and converts the TM mode into the on-chip TE mode. The two outputs are respectively connected to the input of the 1-to-2 optical power splitter for beam splitting. The output optical paths of the 1-to-2 optical power splitter are crossed in pairs and combined by a polarization rotation beam splitter and incident on both ends of the detector.

3. The on-chip polarization-insensitive detector system according to claim 2, characterized in that, The on-chip PRBS device is a polarization rotating beam splitter, which includes a polarization rotating beam splitter for incident light splitting, a polarization rotating beam splitter I for beam combining, and a polarization rotating beam splitter II for beam combining.

4. The on-chip polarization-insensitive detector system according to claim 2, characterized in that, The edge coupler is made of silicon nitride.

5. The on-chip polarization-insensitive detector system according to claim 2, characterized in that, The output of the 1-to-2 optical power splitter is connected to the detector via a waveguide.

6. The on-chip polarization-insensitive detector system according to claim 1, characterized in that, The system includes an edge coupler, a silicon nitride one-to-two optical power splitter, a waveguide interlayer coupler, and a detector. The edge coupler transmits the optical signal from the external optical fiber into the chip. The silicon nitride one-to-two optical power splitter splits the incident optical signal into two output branches, each containing TE and TM modes. Both output branches are transmitted to both ends of the detector through a second waveguide, a waveguide interlayer coupler, and a third waveguide.

7. The on-chip polarization-insensitive detector system according to claim 6, characterized in that, The edge coupler is connected to the silicon nitride one-to-two optical power splitter via a silicon nitride waveguide.

8. The on-chip polarization-insensitive detector system according to claim 6, characterized in that, The second waveguide is a silicon nitride waveguide, and the third waveguide is a silicon waveguide.

9. The on-chip polarization-insensitive detector system according to claim 8, characterized in that, The second and third waveguides have different structures and lengths.

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