A thin film lithium niobate based polarization control device and method

Abstract

The application relates to the field of optical communication technology and discloses a polarization control device and method based on a thin film lithium niobate, which comprises a first optical coupler, a first polarization beam splitting rotator, a polarization measurement component, a 2*2 Mach-Zehnder interferometer, a polarization control system and a lithium niobate optical waveguide arranged on the thin film lithium niobate. After arbitrary input polarized light enters the lithium niobate optical waveguide through the first optical coupler, the input polarized light is converted into TE polarized light through the first polarization beam splitting rotator; the polarization measurement component detects the energy of the TE polarized light and transmits the detection result to the polarization control system; the polarization control system calculates the polarization state of the input polarized light and the transmission matrix between the input polarized light and target output polarized light according to the detection result of the polarization measurement component, calculates a voltage control value according to the transmission matrix, and applies corresponding voltage to the 2*2 Mach-Zehnder interferometer to control the distribution of the TE polarized light in two arms of the 2*2 Mach-Zehnder interferometer and realize polarization control.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of optical communication technology, and more particularly, to a polarization control device and method based on thin film lithium niobate. BACKGROUND

[0002] Polarization state is one of the basic properties of light, and plays an extremely important role in optical communication systems. For example, the transmission capacity can be effectively improved by using polarization multiplexing technology. In a coherent optical communication system, complex digital signal processing is usually required to compensate for the rapid changes in polarization state in the optical fiber. In future ultra-high-speed data transmission systems, relying solely on digital signal processing for polarization state compensation will be a difficult problem. A high-performance automatic polarization control device with an infinite polarization state conversion range can track and stabilize the polarization state at the receiving end, significantly alleviate the pressure on digital signal processing, simplify its algorithm, and reduce power consumption.

[0003] So far, most polarization control devices are based on mechanical rotating wave plates or fiber coils, or on liquid crystal devices, fiber and piezoelectric actuators, wave plates and magneto-optical crystals. The control speed of the former is very slow, and mechanical vibration will introduce instability; the latter can achieve high control speed, but since it relies on bulk optical elements, its control speed is limited to milliseconds or microseconds.

[0004] Lithium niobate is one of the most mature modulator materials, with a linear electro-optic effect of femtosecond order. Applying an electric field to a lithium niobate optical waveguide can change the polarization state of light, and its polarization control speed can reach nanoseconds. Although lithium niobate devices have attracted attention in fast polarization control, the performance of these devices has reached the physical limit supported by traditional lithium niobate waveguides. Existing lithium niobate polarization control devices are still very bulky (more than 5 cm) and have high driving voltages (more than 100 V), such as polarization controllers based on titanium-diffused lithium niobate. These severely limit their applications in communication and sensing fields. SUMMARY

[0005] The present application provides a polarization control device and method based on thin film lithium niobate to overcome the defects of slow control speed, high instability, and large equipment volume in the prior art polarization control.

[0006] To solve the above technical problems, the technical solutions of the present application are as follows:

[0007] A polarization control device based on thin film lithium niobate, comprising a first optical coupler, a first polarization beam splitting rotator, a polarization measurement component, a 2x2 Mach-Zehnder interferometer, a polarization control system, and a lithium niobate optical waveguide arranged on a lithium niobate thin film.

[0008] In this process, any input polarized light enters the lithium niobate optical waveguide through the first optical coupler and is then converted into TE polarized light by the first polarization beam splitter. The polarization measurement component detects the energy of the TE polarized light and transmits the detection result to the polarization control system. Based on the detection result of the polarization measurement component, the polarization control system calculates the polarization state of the input polarized light and the transmission matrix between the input polarized light and the target output polarized light. Based on the transmission matrix, it calculates the voltage control value and then applies the corresponding voltage to the 2×2 Mach-Zehnder interferometer to control the distribution of the TE polarized light in the two arms of the 2×2 Mach-Zehnder interferometer to achieve polarization control.

[0009] As a preferred embodiment, the polarization measurement component includes a first beam splitter for detecting the energy of TE polarized light in a lithium niobate waveguide, a first photodetector for monitoring the polarization state of TE polarized light, and a 2×2 multimode interferometer; wherein the first photodetector is flip-chip bonded above the output grating of the first beam splitter, or the first photodetector is fabricated above the output grating of the first beam splitter using heterogeneous integration technology; the first photodetector is connected to the polarization control system via metal leads.

[0010] As a preferred embodiment, the beam splitter includes a directional coupler or a 1×2 multimode interferometer.

[0011] As a preferred embodiment, the polarization control system includes an analog-to-digital converter, an FPGA control board, and a digital-to-analog converter connected in sequence. The input terminal of the analog-to-digital converter is connected to the output terminal of the polarization measurement component, and the output terminal of the digital-to-analog converter is connected to the voltage control terminal of the 2×2 Mach-Zehnder interferometer.

[0012] As a preferred embodiment, the 2×2 Mach-Zehnder interferometer is an n-order 2×2 Mach-Zehnder interferometer, where n≥2.

[0013] As a preferred embodiment, metal electrodes are respectively provided between the phase-shifting arms and on both sides of the phase-shifting arms of the 2×2 Mach-Zehnder interferometer, and the metal electrodes are connected to the polarization control system through metal leads.

[0014] As a preferred embodiment, the output end of the 2×2 Mach-Zehnder interferometer is provided with a second polarization beam splitter and a second optical coupler; the polarized light output by the polarization modulation of the 2×2 Mach-Zehnder interferometer is combined by the second polarization beam splitter and then output by the second optical coupler.

[0015] As a preferred embodiment, the output end of the 2×2 Mach-Zehnder interferometer is further provided with a second beam splitter and a second photodetector for detecting the energy distribution of the input light in the phase-shifting arm of the 2×2 Mach-Zehnder interferometer. The output end of the second beam splitter is connected to the input end of the second photodetector, and the output end of the second photodetector is connected to the polarization control system through a metal lead.

[0016] As a preferred embodiment, the polarization control device further includes a substrate, on which the lithium niobate thin film is disposed.

[0017] Furthermore, this invention also proposes a polarization control method based on thin-film lithium niobate, applicable to the polarization control device based on thin-film lithium niobate proposed in any of the above-mentioned technical solutions. This includes the following steps:

[0018] The optical signal with arbitrary polarization state input through the first optical coupler is converted into TE polarized light using the first polarization beam splitter rotator;

[0019] A polarization measurement component is used to detect the energy of TE polarized light transmitted in a lithium niobate optical waveguide, and the detection results are transmitted to the polarization control system.

[0020] The polarization control system calculates the polarization state of the input polarized light and the transmission matrix between the input polarized light and the target output polarized light based on the detection results of the polarization measurement component. It then calculates the voltage control value based on the transmission matrix and applies the corresponding voltage to the 2×2 Mach-Zehnder interferometer to control the distribution of the TE polarized light in the two arms of the 2×2 Mach-Zehnder interferometer to achieve polarization control.

[0021] Compared with the prior art, the beneficial effects of the technical solution of the present invention are as follows: The present invention combines a polarization measurement component and a polarization control system to control the phase and intensity modulation of a 2×2 Mach-Zehnder interferometer. Polarization control is achieved by applying a corresponding voltage to the 2×2 Mach-Zehnder interferometer, realizing the transformation of any input polarization state into a fixed polarization output state, or the transformation of any input polarization state into any polarization output state. The present invention utilizes the excellent linear electro-optic effect of lithium niobate, combined with a mature lithium niobate thin film integration platform, and has the advantages of low optical loss, low driving voltage, fast polarization tracking, integration, and miniaturization. Attached Figure Description

[0022] Figure 1 This is a schematic diagram of the polarization control device based on thin-film lithium niobate in Example 1.

[0023] Figure 2 This is a schematic diagram of the input end of the polarization control device based on thin-film lithium niobate in Example 2.

[0024] Figure 3This is a top view of the polarization control device based on thin-film lithium niobate in Example 2.

[0025] Figure 4 This is a schematic diagram of the 2×2 Mach-Zehnder interferometer in Example 3.

[0026] Figure 5 This is a schematic diagram of the output end of the polarization control device based on thin-film lithium niobate in Example 3.

[0027] Figure 6 This is a schematic diagram of the polarization control device based on thin-film lithium niobate in Example 3.

[0028] Figure 7 This is a flowchart of the polarization control method based on thin-film lithium niobate in Example 4.

[0029] Among them, 1-lithium niobate thin film, 2-first optical coupler, 3-first polarization beam splitter rotator, 4-polarization measurement component, 401-first beam splitter, 402-first photodetector, 403-2×2 multimode interferometer, 5-2×2 Mach-Zehnder interferometer, 6-polarization control system, 601-analog-to-digital converter, 602-FPGA control board, 603-digital-to-analog converter, 7-lithium niobate optical waveguide, 8-metal electrode, 9-second polarization beam splitter rotator, 10-second optical coupler, 11-second beam splitter, 12-second photodetector. Detailed Implementation

[0030] The accompanying drawings are for illustrative purposes only and should not be construed as limiting the scope of this patent.

[0031] To better illustrate this embodiment, some parts in the accompanying drawings may be omitted, enlarged, or reduced, and do not represent the actual product dimensions;

[0032] It will be understood by those skilled in the art that certain well-known structures and their descriptions may be omitted in the accompanying drawings.

[0033] The technical solution of the present invention will be further described below with reference to the accompanying drawings and embodiments.

[0034] Example 1

[0035] This embodiment proposes a polarization control device based on thin-film lithium niobate, such as... Figure 1 The diagram shown is a schematic representation of the polarization control device based on thin-film lithium niobate in this embodiment.

[0036] The polarization control device based on thin-film lithium niobate proposed in this embodiment includes a first optical coupler 2, a first polarization beam splitter rotator 3, a polarization measurement component 4, a 2×2 Mach-Zehnder interferometer 5, a polarization control system 6, and a lithium niobate optical waveguide 7 disposed on a lithium niobate thin film 1.

[0037] In this embodiment, the first optical coupler 2 is a polarization-independent end-face coupler, used to couple any input polarized light into the lithium niobate optical waveguide 7 for transmission.

[0038] In this embodiment, the first polarization beam splitter rotator 3 is used to convert any input polarized light into TE polarized light for transmission in the lithium niobate optical waveguide 7.

[0039] In this embodiment, the polarization measurement component 4 is located at the input end of the 2×2 Mach-Zehnder interferometer 5 and is used to detect the energy of TE-polarized light transmitted in the lithium niobate optical waveguide 7. The polarization measurement component 4 is connected to the polarization control system 6 via metal leads, transmitting the detected energy of the TE-polarized light to the polarization control system 6 for calculation and analysis.

[0040] In this embodiment, the polarization control system 6 is used to perform calculations and analyses based on the light information detected by the polarization measurement component 4 to obtain the polarization state of the input light, further calculate the transmission matrix between the input polarized light and the target output polarized light, obtain the voltage control value to be applied to the 2×2 Mach-Zehnder interferometer 5, and apply the corresponding voltage to the 2×2 Mach-Zehnder interferometer 5.

[0041] In this embodiment, the 2×2 Mach-Zehnder interferometer 5 is used to modulate the phase and intensity of TE polarized light transmitted in the lithium niobate optical waveguide 7, so as to convert any input polarization state into a fixed polarization state output, or to convert any input polarization state into any polarization state output.

[0042] In this embodiment, when the 2×2 Mach-Zehnder interferometer 5 modulates the phase and intensity of the input light, the modulation method includes, but is not limited to, electro-optic modulation and thermo-optic modulation.

[0043] Furthermore, in this embodiment, the lithium niobate thin film 1 is disposed on the substrate.

[0044] In the specific implementation process, any input polarized light enters the lithium niobate optical waveguide 7 through the first optical coupler 2, and is then converted into TE polarized light by the first polarization beam splitter rotator 3. The polarization measurement component 4 detects the energy of the TE polarized light and transmits the detection result to the polarization control system 6. The polarization control system 6 calculates the polarization state of the input polarized light and the transmission matrix between the input polarized light and the target output polarized light based on the detection result of the polarization measurement component 4. It calculates the voltage control value based on the transmission matrix and then applies the corresponding voltage to the 2×2 Mach-Zehnder interferometer 5 to control the distribution of the TE polarized light in the two arms of the 2×2 Mach-Zehnder interferometer 5 to achieve polarization control.

[0045] In this embodiment, the phase and intensity modulation of the 2×2 Mach-Zehnder interferometer 5 are controlled by combining the polarization measurement component 4 and the polarization control system 6. Polarization control is achieved by applying a corresponding voltage to the 2×2 Mach-Zehnder interferometer 5, so that any input polarization state can be converted into a fixed polarization state output, such as the TE polarization state, which means that all the input light is output from one output end in the TE polarization state, while the energy of the other output end is 0; or any input polarization state can be converted into any polarization state output.

[0046] The polarization control device based on thin-film lithium niobate in this embodiment utilizes the excellent linear electro-optic effect of lithium niobate and combines it with the mature lithium niobate thin-film integration platform to prepare a fast polarization control device based on thin-film lithium niobate. It has the advantages of low optical loss, low driving voltage, fast polarization tracking, integration, and miniaturization, and is suitable for operation in both O-band and C-band.

[0047] Example 2

[0048] This embodiment is an improvement upon the polarization control device based on thin-film lithium niobate proposed in Embodiment 1.

[0049] The polarization control device based on thin-film lithium niobate proposed in this embodiment includes a first optical coupler 2, a first polarization beam splitter rotator 3, a polarization measurement component 4, a 2×2 Mach-Zehnder interferometer 5, a polarization control system 6, and a lithium niobate optical waveguide 7 disposed on a lithium niobate thin film 1.

[0050] Furthermore, the polarization measurement component 4 in this embodiment includes a first beam splitter 401 for detecting the energy of TE polarized light in the lithium niobate waveguide, a first photodetector 402 for monitoring the polarization state of the TE polarized light, and a 2×2 multimode interferometer 403. The first photodetector 402 is flip-chip welded above the output grating of the first beam splitter 401, or the first photodetector 402 is fabricated above the output grating of the first beam splitter 401 using heterogeneous integration technology. The first photodetector 402 is connected to the polarization control system 6 via metal leads. The 2×2 multimode interferometer 403 mixes and splits the two input beams, performs interference, and, in conjunction with the first polarization beam rotator 3, the first beam splitter 401, and the first photodetector 402, jointly realizes the function of polarization state measurement.

[0051] like Figure 2 The diagram shown is a schematic representation of the input terminal of the polarization control device based on thin-film lithium niobate in this embodiment.

[0052] The beam splitter is either a directional coupler or a 1×2 multimode interferometer with a 1:19 splitting ratio.

[0053] In one specific embodiment, a two-stage 2×2 Mach-Zehnder interferometer 5 is used. The input end of the 2×2 Mach-Zehnder interferometer 5 is equipped with four first beam splitters 401 with directional couplers, which respectively detect the energy of the transmitted light in the lithium niobate optical waveguide 7 at the corresponding positions, and transmit the information of the transmitted light to the polarization control system 6 through the first photodetector 402 above the output grating. The polarization control system 6 can obtain the polarization state of the input light by calculation and analysis.

[0054] like Figure 3 The image shown is a top view of the polarization control device based on thin-film lithium niobate in this embodiment.

[0055] Furthermore, the polarization control system 6 in this embodiment includes an analog-to-digital converter 601, an FPGA control board 602, and a digital-to-analog converter 603 connected in sequence. The input terminal of the analog-to-digital converter 601 is connected to the output terminal of the polarization measurement component 4, and the output terminal of the digital-to-analog converter 603 is connected to the voltage control terminal of the 2×2 Mach-Zehnder interferometer 5.

[0056] In this embodiment, the analog-to-digital converter 601 converts the optical information detected by the polarization measurement component 4 into a digital signal for calculation and analysis on the FPGA control board 602. Specifically, the FPGA control board 602 is pre-configured with algorithms for calculating and analyzing the energy of TE polarized light, calculating the transmission matrix between the input polarized light and the target output polarized light, and calculating the voltage control value based on the transmission matrix and the energy of the TE polarized light.

[0057] After the FPGA control board 602 completes the calculation of the voltage control value, the control signal is converted into an analog signal by the digital-to-analog converter 603, and the corresponding voltage is applied to the 2×2 Mach-Zehnder interferometer 5 to control the distribution of TE polarized light in the two arms of the 2×2 Mach-Zehnder interferometer 5 to achieve polarization control.

[0058] Example 3

[0059] This embodiment is an improvement on the polarization control device based on thin-film lithium niobate proposed in Embodiment 1 or 2.

[0060] The polarization control device based on thin-film lithium niobate proposed in this embodiment includes a first optical coupler 2, a first polarization beam splitter rotator 3, a polarization measurement component 4, a 2×2 Mach-Zehnder interferometer 5, a polarization control system 6, and a lithium niobate optical waveguide 7 disposed on a lithium niobate thin film 1.

[0061] In this embodiment, metal electrodes 8 are respectively disposed between the phase-shifting arms and on both sides of the phase-shifting arms of the 2×2 Mach-Zehnder interferometer 5. The metal electrodes 8 are connected to the polarization control system 6 through metal leads. The polarization control system 6 controls the voltage of the metal electrodes 8 through the metal leads to control the distribution of transmitted light in the two arms of the 2×2 Mach-Zehnder interferometer 5, thereby achieving polarization control.

[0062] like Figure 4 The diagram shown is a schematic representation of the 2×2 Mach-Zehnder interferometer 5 in this embodiment.

[0063] Furthermore, in this embodiment, the 2×2 Mach-Zehnder interferometer 5 is an n-order 2×2 Mach-Zehnder interferometer 5, where n≥2.

[0064] The number of levels of the Mach-Zehnder interferometer in this embodiment is set according to the actual application scenario, so as to achieve endless automatic control and continuous tracking of all possible rapidly changing polarization states.

[0065] In one specific embodiment, a two-stage 2×2 Mach-Zehnder interferometer 5 is used. The input end of the 2×2 Mach-Zehnder interferometer 5 is equipped with four first beam splitters 401 using directional couplers. These splitters detect the energy of the transmitted light in the lithium niobate optical waveguide 7 at corresponding positions and transmit the information of the transmitted light to the polarization control system 6 via a first photodetector 402 above its output grating. Based on the detection results of the polarization measurement component 4, the polarization control system 6 calculates the polarization state of the input polarized light and the transmission matrix between the input polarized light and the target output polarized light. Based on the transmission matrix, it calculates the voltage control value and then applies the corresponding voltage to the two-stage 2×2 Mach-Zehnder interferometer 5 to control the distribution of the TE polarized light in both arms of the 2×2 Mach-Zehnder interferometer 5, thus achieving polarization control.

[0066] Furthermore, the output end of the 2×2 Mach-Zehnder interferometer 5 is provided with a second polarization beam splitter 9 and a second optical coupler 10; the polarized light output by the polarization modulation of the 2×2 Mach-Zehnder interferometer 5 is combined by the second polarization beam splitter 9 and then output by the second optical coupler 10.

[0067] The second polarization beam splitter rotator 9 is used for beam combining and can convert any input polarization state into any output polarization state.

[0068] In the specific implementation process, the polarization control system 6 calculates the ratio of the transmitted light in the two arms of the nth-stage 2×2 Mach-Zehnder interferometer 5 before the beam combining in the second polarization beam splitter rotator 9 according to the polarization state of the target output polarized light. It then adjusts the voltage control value based on the ratio of the transmitted light in the two arms of the nth-stage 2×2 Mach-Zehnder interferometer 5 and applies it to the 2×2 Mach-Zehnder interferometer 5 to achieve phase modulation of the input polarized light, thereby realizing the transformation of any input polarization state into any target polarization state and outputting it.

[0069] Furthermore, the output end of the 2×2 Mach-Zehnder interferometer 5 is also provided with a second beam splitter 11 and a second photodetector 12 for detecting the energy distribution of the input light in the phase-shifting arm of the 2×2 Mach-Zehnder interferometer. The output end of the second beam splitter 11 is connected to the input end of the second photodetector 12, and the output end of the second photodetector 12 is connected to the polarization control system 6 through a metal lead.

[0070] like Figure 5 The diagram shown is a schematic representation of the output of the polarization control device based on thin-film lithium niobate in this embodiment.

[0071] The second beam splitter 11 and the second photodetector 12 are used to monitor the polarization state of the output light and feed the monitoring results back to the polarization control system 6 in a timely manner to ensure that the output light is in the target polarization state.

[0072] In another embodiment, a 2×2 Mach-Zehnder interferometer of order n=3 is used. For example... Figure 6 The diagram shown is a schematic representation of the polarization control device based on thin-film lithium niobate in this embodiment.

[0073] In the specific implementation process, any input polarized light is converted into TE polarized light and passes through the first and second stage 2×2 Mach-Zehnder interferometers 5 in sequence. It is then transmitted in one arm of the output end of the second stage 2×2 Mach-Zehnder interferometer 5. The polarization control system 6 then controls the phase modulation of the third stage 2×2 Mach-Zehnder interferometer 5. The polarization control system 6 controls the distribution of the transmitted light in the two arms of the third stage 2×2 Mach-Zehnder interferometer 5 according to the target output polarization state. Finally, the target output polarized light is obtained by combining the beams through the second polarization beam splitter rotator 9.

[0074] Example 4

[0075] This embodiment proposes a polarization control method based on thin-film lithium niobate, applicable to any of the polarization control devices based on thin-film lithium niobate proposed in Embodiments 1-3. For example... Figure 7 The diagram shown is a flowchart of the polarization control method based on thin-film lithium niobate in this embodiment.

[0076] The polarization control method based on thin-film lithium niobate proposed in this embodiment includes the following steps:

[0077] S1. The optical signal with arbitrary polarization state input through the first optical coupler 2 is converted into TE polarized light by the first polarization beam splitter rotator 3.

[0078] S2. The polarization measurement component 4 is used to detect the energy of the TE polarized light transmitted in the lithium niobate optical waveguide 7, and the detection result is transmitted to the polarization control system 6.

[0079] S3. The polarization control system 6 calculates the polarization state of the input polarized light and the transmission matrix between the input polarized light and the target output polarized light based on the detection results of the polarization measurement component 4. It then calculates the voltage control value based on the transmission matrix and applies the corresponding voltage to the 2×2 Mach-Zehnder interferometer 5 to control the distribution of the TE polarized light in the two arms of the 2×2 Mach-Zehnder interferometer 5 to achieve polarization control.

[0080] Furthermore, after the polarization control system 6 applies a corresponding voltage to the 2×2 Mach-Zehnder interferometer 5, the following steps are also included:

[0081] The second polarization beam splitter rotator 9 is used to combine the transmitted light output from the 2×2 Mach-Zehnder interferometer 5. At the same time, the second beam splitter 11 and the second photodetector 12 are used to detect the polarized light output by the polarization modulation of the 2×2 Mach-Zehnder interferometer 5. The energy distribution of the input light in the phase-shifting arm of the 2×2 Mach-Zehnder interferometer is detected and fed back to the polarization control system 6. The polarization control system 6 adjusts the voltage control value according to the output feedback to ensure that any input polarization state is converted into any target polarization state and output.

[0082] The same or similar labels correspond to the same or similar parts;

[0083] The terms used to describe positional relationships in the accompanying drawings are for illustrative purposes only and should not be construed as limiting this patent.

[0084] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the implementation of the present invention. Those skilled in the art can make other variations or modifications based on the above description. It is neither necessary nor possible to exhaustively describe all embodiments here. 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 claims of the present invention.

Claims

1. A polarization control device based on thin-film lithium niobate, characterized in that, The system includes a first optical coupler (2), a first polarization beam splitter (3), a polarization measurement component (4), a 2×2 Mach-Zehnder interferometer (5), a polarization control system (6), and a lithium niobate optical waveguide (7) disposed on a lithium niobate thin film (1), wherein: After any input polarized light passes through the first optical coupler (2) and enters the lithium niobate optical waveguide (7), it is converted into TE polarized light by the first polarization beam splitter (3). The polarization measurement component (4) performs energy detection on the TE polarized light and transmits the detection result to the polarization control system (6); The polarization measurement component (4) includes a first beam splitter (401) for detecting the energy of TE polarized light in a lithium niobate waveguide, a first photodetector (402) for monitoring the polarization state of TE polarized light, and a 2×2 multimode interferometer (403); wherein the first photodetector (402) is flip-chip welded above the output grating of the first beam splitter (401), or the first photodetector (402) is fabricated above the output grating of the first beam splitter (401) using heterogeneous integration technology; the first photodetector (402) is connected to the polarization control system (6) via metal leads; The first beam splitter (401) includes a directional coupler or a 1×2 multimode interferometer; The polarization control system (6) calculates the polarization state of the input polarized light and the transmission matrix between the input polarized light and the target output polarized light based on the detection results of the polarization measurement component (4). It calculates the voltage control value based on the transmission matrix and then applies the corresponding voltage to the 2×2 Mach-Zehnder interferometer (5) to control the distribution of the TE polarized light in the two arms of the 2×2 Mach-Zehnder interferometer (5) to achieve polarization control. The polarization control system (6) includes an analog-to-digital converter (601), an FPGA control board (602), and a digital-to-analog converter (603) connected in sequence. The input terminal of the analog-to-digital converter (601) is connected to the output terminal of the polarization measurement component (4), and the output terminal of the digital-to-analog converter (603) is connected to the voltage control terminal of the 2×2 Mach-Zehnder interferometer (5).

2. The polarization control device based on thin-film lithium niobate according to claim 1, characterized in that, The 2×2 Mach-Zehnder interferometer (5) is an n-order 2×2 Mach-Zehnder interferometer (5), where n≥2.

3. The polarization control device based on thin-film lithium niobate according to claim 1, characterized in that, Metal electrodes (8) are respectively provided between the phase-shifting arms of the 2×2 Mach-Zehnder interferometer (5) and on both sides of the phase-shifting arms. The metal electrodes (8) are connected to the polarization control system (6) through metal leads.

4. The polarization control device based on thin-film lithium niobate according to claim 1, characterized in that, The output end of the 2×2 Mach-Zehnder interferometer (5) is provided with a second polarization beam splitter (9) and a second optical coupler (10); the polarized light output by the polarization modulation of the 2×2 Mach-Zehnder interferometer (5) is combined by the second polarization beam splitter (9) and then output by the second optical coupler (10).

5. The polarization control device based on thin-film lithium niobate according to claim 4, characterized in that, The output end of the 2×2 Mach-Zehnder interferometer (5) is also provided with a second beam splitter (11) and a second photodetector (12) for detecting the energy distribution of the input light in the phase-shifting arm of the 2×2 Mach-Zehnder interferometer. The output end of the second beam splitter (11) is connected to the input end of the second photodetector (12), and the output end of the second photodetector (12) is connected to the polarization control system (6) through a metal lead.

6. The polarization control device based on thin-film lithium niobate according to any one of claims 1 to 5, characterized in that, The polarization control device also includes a substrate, on which the lithium niobate thin film (1) is disposed.

7. A polarization control method based on thin-film lithium niobate, applied to the polarization control device based on thin-film lithium niobate as described in any one of claims 1 to 6, characterized in that, Includes the following steps: The optical signal with arbitrary polarization state input through the first optical coupler (2) is converted into TE polarized light by the first polarization beam splitter (3); The energy of TE polarized light transmitted in the lithium niobate optical waveguide (7) is detected by a polarization measurement component (4), and the detection result is transmitted to the polarization control system (6). The polarization control system (6) calculates the polarization state of the input polarized light and the transmission matrix between the input polarized light and the target output polarized light based on the detection results of the polarization measurement component (4). It then calculates the voltage control value based on the transmission matrix and applies the corresponding voltage to the 2×2 Mach-Zehnder interferometer (5) to control the distribution of the TE polarized light in the two arms of the 2×2 Mach-Zehnder interferometer (5) to achieve polarization control.

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