A dynamic polarization controller based on silicon-based optoelectronic chip

Abstract

The application discloses a dynamic polarization controller based on a silicon-based optoelectronic chip, which can lock an arbitrary polarization state light field to an arbitrary required polarization state light field. The controller couples the light of the arbitrary polarization state light field from a single-mode optical fiber into the chip through a first end face coupling structure via a first high numerical aperture optical fiber; after passing through a first polarization rotation beam splitter (PRS), the TE0 mode and TM0 mode light fields entering the chip are both converted into TE0 mode light fields; after polarization locking by adopting a waveguide 0° / 45° / 0° structure, the two TE0 mode light fields are combined into one by a second polarization rotation beam splitter and are converted into TE0 mode and TM0 mode light fields, and then are output to a second high numerical aperture optical fiber via a second end face coupling structure and are relayed into a single-mode optical fiber. The waveguide 0° / 45° / 0° structure adopts an electrically controlled phase shifter, and combines an analog annealing algorithm, a gradient algorithm and other algorithms to automatically lock the polarization state of the light.

Description

Technical Field

[0001] This invention relates to the field of quantum secure communication, and in particular to a dynamic polarization controller based on a silicon-based optoelectronic chip. Background Technology

[0002] Continuous-variable quantum secure communication systems employ time-division multiplexing and polarization multiplexing techniques to transmit the signal optical field and the local oscillator optical field in the same long-distance single-mode optical fiber. During transmission, external factors such as temperature and humidity can cause birefringence in the single-mode fiber, leading to changes in the polarization state. At the receiving end, Bob needs to use a dynamic polarization controller to restore and lock the polarization of the two optical fields to a linear polarization state. After locking, the two optical fields are re-split into the signal optical field path and the local oscillator optical path by a polarization beam splitter. Traditional polarization controllers include three-loop polarization controllers and electrically controlled polarization controllers. These polarization controllers are typically large, have low response rates, and high power consumption.

[0003] Silicon-based optoelectronics emerged in the 1980s. By utilizing technologies on silicon-based integrated circuits to design, manufacture, and package optical devices and optoelectronic integrated circuits, it has achieved integrated circuit-level integration, manufacturability, and scalability, thus achieving breakthroughs in cost, power consumption, and size. Some research groups have already developed dynamic polarization controllers based on silicon-based chips. The paper "Siliconphotonics integrated dynamic polarization controller. Chin. Opt. Lett., 041301, 2022." uses four locking structures at 0° / 45° / 0° / 45°. This paper uses a two-dimensional grating to couple the optical field between the single-mode fiber and the silicon-based optoelectronic chip, resulting in significant coupling loss and reduced system efficiency in detecting the optical field. Furthermore, it does not fully utilize the phase-determining characteristics of the thermal phase shifter on the silicon-based optoelectronic chip and does not employ a method of simultaneous dual-phase control in individual 0° or 45° structures. Summary of the Invention

[0004] This invention addresses the problems of existing dynamic polarization controllers by designing a silicon-based optoelectronic chip-based dynamic polarization controller that can lock an arbitrary polarization state light field to an arbitrary polarization state light field. The device employs end-face coupling technology and polarization rotation beam splitting technology to effectively reduce coupling loss and achieve low-loss beam splitting and combining of polarized light fields. An arrayed fiber optic coupling interface (FA) is used to achieve same-side end-face coupling of the input and output ports, facilitating coupling and packaging. Endless polarization control is achieved based on the equivalent waveguide 0° / 45° / 0° structure of the electrically controlled phase shifter on the silicon-based optoelectronic chip. It features low cost, low power consumption, and small size. Therefore, this invention provides a dynamic polarization controller based on a silicon-based optoelectronic chip.

[0005] In order to achieve the expected results of the theoretical analysis and experimental verification of the above technical solutions, the present invention adopts the following technical solutions:

[0006] A dynamic polarization controller based on a silicon-based optoelectronic chip includes a silicon-based optoelectronic chip with an input / output structure connected to its side. The silicon-based optoelectronic chip has a first end-face coupling structure connected to the input end of the input / output structure and a second end-face coupling structure connected to the output end of the input / output structure. A first polarization rotation beam splitter, a first polarization control structure, a second polarization control structure, a third polarization control structure, and a second polarization rotation beam splitter are sequentially connected between the first end-face coupling structure and the second end-face coupling structure.

[0007] As a further improvement to the above scheme, the input-output structure includes an array fiber FA port, a first fiber connector, and a second fiber connector. The array fiber FA port includes a first high numerical aperture fiber as an input end and a second high numerical aperture fiber as an output end. One end of the first high numerical aperture fiber is connected to a first end face coupling structure, and the other end is connected to the first fiber connector through a single-mode fiber. One end of the second high numerical aperture fiber is connected to a second end face coupling structure, and the other end is connected to the second fiber connector through a single-mode fiber.

[0008] As a further improvement to the above scheme, both the first end-face coupling structure and the second end-face coupling structure are constructed as trapezoidal end-face coupling structures.

[0009] As a further improvement to the above scheme, the first polarization control structure includes a first electrically controlled phase shifter and a second electrically controlled phase shifter, which implement 0° polarization control function; the second polarization control structure includes a first 50 / 50 coupler, a third electrically controlled phase shifter, a fourth electrically controlled phase shifter, and a second 50 / 50 coupler, which implement 45° polarization control function; the third polarization control structure includes a fifth electrically controlled phase shifter and a sixth electrically controlled phase shifter, which implement 0° polarization control function.

[0010] As a further improvement to the above scheme, the first electrically controlled phase shifter is powered by the first and second pads; the second electrically controlled phase shifter is powered by the third and second pads, with the second pad being a common terminal; the third electrically controlled phase shifter is powered by the fourth and fifth pads; the fourth electrically controlled phase shifter is powered by the sixth and fifth pads, with the fifth pad being a common terminal; the fifth electrically controlled phase shifter is powered by the seventh and eighth pads; and the sixth electrically controlled phase shifter is powered by the ninth and eighth pads, with the eighth pad being a common terminal.

[0011] As a further improvement to the above scheme, the first polarization rotating beam splitter is composed of a first polarization rotating part and a first polarization splitting part; the first polarization rotating part is composed of a first etched waveguide and a first transition waveguide front half; the first polarization splitting part is composed of a first transition waveguide rear half and a first thermally insulating waveguide; the second polarization rotating beam splitter is composed of a second polarization splitting part and a second polarization rotating part; the second polarization splitting part is composed of a second transition waveguide rear half and a second thermally insulating waveguide; the second polarization rotating part is composed of a second etched waveguide and a second transition waveguide front half.

[0012] As a further improvement to the above scheme, a first compensation waveguide is connected between the first polarization control structure and the second polarization control structure to ensure that the waveguide lengths from the first polarization beamsplitter to the first 50 / 50 coupler are equal; a second compensation waveguide is connected between the second polarization control structure and the second polarization rotating beamsplitter to ensure that the waveguide lengths from the second 50 / 50 coupler to the second polarization beamsplitter are equal.

[0013] A control method for a dynamic polarization controller based on a silicon-based optoelectronic chip includes the following steps:

[0014] Step 1: An arbitrary polarization state optical field in an external single-mode fiber is input to a first high numerical aperture fiber via the first fiber connector in the input-output structure for mode conversion. After mode matching, it is transmitted to the first end-face coupling structure, where it is further converted and transmitted to the first polarization rotating beam splitter. The arbitrary polarization state optical field entering the first polarization rotating beam splitter is divided into a TM mode fundamental mode optical field TM0 mode and a TE mode fundamental mode optical field TE0 mode. The TM0 mode optical field is converted into a higher-order TE mode optical field TE1 mode after the first polarization rotating part, while the TE0 mode optical field does not undergo conversion. Then, the TE1 mode optical field and the TE0 mode optical field enter the first polarization beam splitting part. The TE0 mode optical field is output along the first transition waveguide without mode conversion, and is output from the first transition waveguide port of the first polarization rotating beam splitter. The TE1 mode optical field is coupled from the first transition waveguide to the first adiabatic waveguide, and is output from the first adiabatic waveguide port of the first polarization rotating beam splitter, with its mode converted to TE0. Two beams of light with TE0 mode polarization are output from the first polarization rotating beam splitter.

[0015] Step 2: The two TE0 mode light fields output from the first polarization rotating beam splitter sequentially enter the first polarization control structure, the second polarization control structure, and the third polarization control structure; the first polarization control structure, the second polarization control structure, and the third polarization control structure all use electronically controlled phase shifters to generate phase delay.

[0016] Step 3: After passing through three polarization-locking structures, the two TE0 mode light fields output from the third polarization control structure enter the second polarization rotating beam splitter. The light from the sixth electrically controlled phase shifter enters the second transition waveguide, and the light from the fifth electrically controlled phase shifter enters the second thermally adiabatic waveguide. The TE0 mode light in the second transition waveguide continues to propagate along the second transition waveguide in TE0 mode without changing its mode. The TE0 mode light in the second thermally adiabatic waveguide is coupled from the second thermally adiabatic waveguide to the second transition waveguide in the second polarization beam splitting section, and its mode is converted to TE1 mode. The two beams are combined into one beam and then enter the second polarization rotating section. The second polarization rotating section converts the TE1 mode to TM0 mode, while the TE0 mode remains unchanged. Afterward, the light in both TM0 and TE0 modes is input into the second end-face coupling structure. After mode conversion and matching, it is output to the second high numerical aperture fiber in the input-output structure. After mode conversion again, it is output through the second fiber connector.

[0017] Compared with the prior art, the present invention has the following advantages:

[0018] 1. This invention employs an array end-face coupling structure that enables mode matching and coupling encapsulation with arrayed high numerical aperture (HFA) optical fibers. The end-face coupling structure achieves good mode matching between the mode radius of the waveguide within the chip and the mode radius of the HFA fiber, reducing the loss caused by the difference in their mode radii and achieving a low coupling loss of approximately 2 dB. In the 1550 nm band, the mode size of a single-mode waveguide is approximately 0.4 μm; after the end-face coupling structure, the mode radius expands to 3.5 μm. This size matches the 3.5 μm mode size of the HFA fiber.

[0019] 2. This invention employs a waveguide 0° / 45° / 0° structure to lock the polarization state of the optical field. Through three polarization locking structures, it achieves uninterrupted control of the polarization state, locking any input polarization state to any desired output polarization state, and achieving a dynamic extinction ratio greater than 25dB. This dynamic polarization controller fully utilizes the precise phase control characteristics of an electronically controlled phase shifter and the dual-voltage control capability of the same polarization control structure, eliminating the need for a 0° / 45° / 0° / 45° structure.

[0020] 3. The dynamic polarization controller designed in this invention adopts silicon-based optoelectronic integration technology. Compared with traditional dynamic polarization controllers, it has the advantages of small size, low power consumption, and low cost, which facilitates large-scale production and application in quantum information technology fields such as quantum communication. Attached Figure Description

[0021] Figure 1 This is a schematic diagram of the structure of a dynamic polarization controller based on a silicon-based optoelectronic chip in this invention.

[0022] Figure 2 This is a schematic diagram of the end-face coupling structure in this invention;

[0023] Figure 3 This is a schematic diagram of the structure of the first polarization rotating beam splitter in this invention;

[0024] Figure 4 This is a schematic diagram of the structure of the second polarization rotating beam splitter in this invention;

[0025] Figure 5 This is a diagram of the experimental setup in an embodiment of the present invention;

[0026] Figure 6 : This is a diagram showing the relationship between power consumption and phase shift of the electronically controlled phase shifter in this embodiment of the invention;

[0027] Figure 7 : A graph showing the polarization locking results obtained after conducting experiments using specific embodiments of the present invention;

[0028] In the diagram: 1. Silicon-based optoelectronic chip; 2. Input / output structure; 3. First end-face coupling structure; 4. First polarization rotation beam splitter; 5. First polarization control structure; 6. Second polarization control structure; 7. Third polarization control structure; 8. Second polarization rotation beam splitter; 9. Second end-face coupling structure; 10. Arrayed fiber FA port; 11. First high numerical aperture fiber; 12. Second high numerical aperture fiber; 13. First fiber connector; 14. Second fiber connector; 15. First electrically controlled phase shifter; 16. Second electrically controlled phase shifter; 17. First 50 / 50 coupler; 18. Third electrically controlled phase shifter; 19. Fourth electrically controlled phase shifter; 20. Second 50 / 50 coupler; 21. Fifth electrically controlled phase shifter; 22. Sixth electrically controlled phase shifter; 23. Third pad; 24. First pad; 25. Second pad; 26. Sixth pad; 27. Fourth pad. Fifth pad 28, Ninth pad 29, Seventh pad 30, Eighth pad 31, First compensation waveguide 32, Second compensation waveguide 33, First polarization rotation section 34, First polarization beam splitter section 35, Second polarization beam splitter section 36, Second polarization rotation section 37, 1550nm fiber pigtail DFB laser 38, Adjustable optical attenuator 39, 50 / 50 beam splitter 40, First power meter 41, Manual polarization controller 42, Polarization beam splitter 43, Second power meter 44, Photodetector 45, USB6259 acquisition card acquisition end 46, Computer control end 47, USB6259 acquisition card output end 48, First etched waveguide 49, First transition waveguide 50, First thermal insulation waveguide 51, Second etched waveguide 52, Second transition waveguide 53, Second thermal insulation waveguide 54. Detailed Implementation

[0029] To further illustrate the technical solution of the present invention, within the scope of protection described above, we will further explain the specific implementation of the present invention by selecting the optimal embodiments below.

[0030] This invention provides a dynamic polarization controller based on a silicon-based optoelectronic chip, comprising a silicon-based optoelectronic chip 1, with an input / output structure 2 connected to the side of the chip 1. The input / output structure 2 includes an array fiber optic FA port 10, a first fiber optic connector 13, and a second fiber optic connector 14. The array fiber optic FA port 10 includes a first high numerical aperture fiber 11 as the input end and a second high numerical aperture fiber 12 as the output end. One end of the first high numerical aperture fiber 11 is connected to a first end-face coupling structure 3, and the other end is connected to the first fiber optic connector 13 via a single-mode fiber. The first high numerical aperture fiber 11, as the input fiber, performs optical coupling with the first end-face coupling structure 3 to achieve mode matching and polarize any arbitrary polarization state. The optical field is input into the first end-face coupling structure 3; one end of the second high numerical aperture fiber 12 is connected to the second end-face coupling structure 9, and the other end is connected to the second fiber connector 14 through a single-mode fiber; the second high numerical aperture fiber 12 serves as the output fiber and couples with the second end-face coupling structure 9 to achieve mode matching, outputting the locked arbitrary polarization state optical field from the second end-face coupling structure 9 to the second high numerical aperture fiber 12. Both fiber connectors use general FC / APC connectors, and both the first end-face coupling structure 3 and the second end-face coupling structure 9 are constructed as trapezoidal end-face coupling structures, which increases the very small mode radius in the silicon waveguide, thereby solving the mode matching and refractive index matching problems and reducing coupling loss.

[0031] like Figure 1 As shown, the silicon-based optoelectronic chip 1 is fabricated using CSiP180Al active current technology, based on an SOI substrate, with a 2μm buried oxide (BOX) layer and a 220nm top silicon layer. Testing revealed that the overall loss of the dynamic polarization controller based on this silicon-based optoelectronic chip 1 is 5.35dB, and the end-face coupling loss is 2dB, significantly lower than the losses of other dynamic polarization controllers on the market.

[0032] like Figure 2As shown, the first end-face coupling structure 3 and the second end-face coupling structure 9 are composed of a silicon waveguide with a length of 400 μm, a width of 0.14 μm at one end, a width of 0.45 μm at the other end, and a thickness of 0.22 μm. The 0.14 μm wide end is located at the edge of the silicon-based optoelectronic chip 1. The distance between the first end-face coupling structure 3 and the second end-face coupling structure 9 is 127 μm. The distance between the first high numerical aperture fiber 11 and the second high numerical aperture fiber 12 is also 127 μm. The first high numerical aperture fiber 11 is optically coupled to the first end-face coupling structure 3, and the second high numerical aperture fiber 12 is optically coupled to the second end-face coupling structure 9. After optical coupling, the two are encapsulated together by UV photopolymerization. The first polarization rotating beam splitter 4 and the second polarization rotating beam splitter 8 are connected to the 0.45 μm wide ends of the first end-face coupling structure 3 and the second end-face coupling structure 9, respectively.

[0033] A first polarization rotating beam splitter 4, a first polarization control structure 5, a second polarization control structure 6, a third polarization control structure 7, and a second polarization rotating beam splitter 8 are sequentially connected between the first end-face coupling structure 3 and the second end-face coupling structure 9.

[0034] The first polarization control structure 5 includes a first electrically controlled phase shifter 15 and a second electrically controlled phase shifter 16. The first electrically controlled phase shifter 15 and the second electrically controlled phase shifter 16 can achieve 0° polarization control. The first electrically controlled phase shifter 15 is powered by a first pad 24 and a second pad 25, and the second electrically controlled phase shifter 16 is powered by a third pad 23 and a second pad 25. Pad 25 is a common terminal. The second polarization control structure 6 includes a first 50 / 50 coupler 17, a third electrically controlled phase shifter 18, a fourth electrically controlled phase shifter 19, and a second 50 / 50 coupler 20. The first electrically controlled phase shifter 15, the first 50 / 50 coupler 17, the third electrically controlled phase shifter 18, the fourth electrically controlled phase shifter 19, and the second 50 / 50 coupler 20 are all connected together. 9. The second 50 / 50 coupler 20 and the sixth electrically controlled phase shifter 22 can realize the 45° polarization control function. The third electrically controlled phase shifter 18 is powered by the fourth pad 27 and the fifth pad 28. The fourth electrically controlled phase shifter 19 is powered by the sixth pad 26 and the fifth pad 28, with the fifth pad 28 being the common terminal. The third polarization control structure 7 includes the fifth electrically controlled phase shifter 21 and the sixth electrically controlled phase shifter 22. The fifth electrically controlled phase shifter 21 and the sixth electrically controlled phase shifter 22 can realize the 0° polarization control function. The fifth electrically controlled phase shifter 21 is powered by the seventh pad 30 and the eighth pad 31. The sixth electrically controlled phase shifter 22 is powered by the ninth pad 29 and the eighth pad 31, with the eighth pad 31 being the common terminal.

[0035] In the Jones calculus, the stressed fiber can be represented by two transformation matrices M0 and M45, as shown in equation (1):

[0036]

[0037] α and β are the phase delay caused by birefringence in the stressed fiber; i represents the imaginary part; e represents the exponential form.

[0038] The three polarization-locking structures can then be described using the Jones matrix product:

[0039]

[0040] α, β, and γ represent the phase delay caused by birefringence in the stressed fiber; i represents the imaginary part; e represents the exponential form.

[0041] Matrix M45 can be transformed into the product of a 50 / 50 coupler matrix, an M0 type matrix, and another 50 / 50 coupler matrix, as shown in equation (3).

[0042]

[0043] In the formula, β represents the phase delay; i represents the imaginary part; and e represents the exponential form.

[0044] Therefore, these three transformation matrices (0° / 45° / 0°) are converted into an equivalent waveguide structure on a silicon-based optoelectronic chip, such as... Figure 1 As shown, a parallel waveguide-controlled phase shifter is used to form a dual-channel polarization controller. The first and second electronically controlled phase shifters 15 and 16 are used to generate the α phase delay; the third and fourth electronically controlled phase shifters 18 and 19 are used to generate the β phase delay; and the fifth and sixth electronically controlled phase shifters 21 and 22 are used to generate the γ phase delay. This increases the flexibility of the control method, enables precise phase control, and simplifies the reset process when the phase reaches saturation.

[0045] The first polarization rotating beam splitter 4 is composed of a first polarization rotating part 34 and a first polarization beam splitting part 35. The first polarization rotating part 34 is composed of a first etched waveguide 49 and the front half of a first transition waveguide 50. The first polarization beam splitting part 35 is composed of the rear half of the first transition waveguide 50 and a first thermally insulating waveguide 51. In the first polarization rotating beam splitter 4, the direction of light propagation is from left to right. The light first passes through the first polarization rotating structure 34 and then passes through the first polarization beam splitting part 35.

[0046] The second polarization rotating beam splitter 8 is composed of a second polarization beam splitting section 36 and a second polarization rotating section 37; the second polarization beam splitting section 36 is composed of the rear half of the second transition waveguide 53 and the second thermally insulating waveguide 54; the second polarization rotating section 37 is composed of the second etched waveguide 52 and the front half of the second transition waveguide 53; in the second polarization rotating beam splitter 8, the direction of light propagation is from right to left, and the light first passes through the second polarization beam splitting section 36 and then through the second polarization rotating section 37.

[0047] like Figure 3 and Figure 4 As shown, when light enters the silicon-based optoelectronic chip 1 from the first end-face coupling structure 3, the arbitrary polarization state light field entering the first polarization rotating beam splitter 4 is divided into the fundamental mode light field TM0 of TM mode and the fundamental mode light field TE0 of TE mode. The TM0 mode light field is converted into the higher-order mode light field TE1 of TE mode through the first polarization rotating part 34, while the TE0 mode light field does not undergo conversion. Then, the TE1 mode light field and the TE0 mode light field enter the first polarization beam splitter 35. The TE0 mode light field is output along the first transition waveguide 50 without mode conversion, and is output from the first transition waveguide 50 port of the first polarization rotating beam splitter 4. The TE1 mode light field is coupled from the first transition waveguide 50 to the first adiabatic waveguide 51, and is output from the first adiabatic waveguide 51 port of the first polarization rotating beam splitter 4, with the mode converted to TE0. Two beams of light with TE0 mode polarization are output from the first polarization rotating beam splitter 4. After passing through three polarization rotating parts... After the vibration locking structure is completed, the two TE0 mode light fields output from the third polarization control structure 7 enter the second polarization rotating beam splitter 8. The light from the sixth electrically controlled phase shifter 22 enters the second transition waveguide 53, and the light from the fifth electrically controlled phase shifter 21 enters the second thermally adiabatic waveguide 54. The TE0 mode light in the second transition waveguide 53 continues to propagate along the second transition waveguide 53 in the TE0 mode without changing its mode. The TE0 mode light in the second thermally adiabatic waveguide 54 is coupled from the second thermally adiabatic waveguide 54 to the second transition waveguide 53 in the second polarization beam splitting section 36, and its mode is converted to TE1 mode. The two beams are combined into one beam and then enter the second polarization rotating section 37. The second polarization rotating section 37 converts the TE1 mode to the TM0 mode, while the TE0 mode remains unchanged. The beams are output from the second polarization rotating beam splitter 8 to the second end face coupling structure 9 in both TM0 and TE0 modes.

[0048] The first end-face coupling structure 3 and the first polarization rotating beam splitter 4 are combined to replace the two-dimensional grating input structure, coupling light into the silicon-based optoelectronic chip 1 and rotating its polarization state so that any polarized light field enters the polarization-locking structure in TE0 mode. The second polarization rotating beam splitter 8 and the second end-face coupling structure 9 are combined to replace the two-dimensional grating output structure, merging the two locked TE0 mode beams of any polarized light into one beam and converting part of the light field into TM0 mode, outputting from the silicon-based optoelectronic chip 1 in both TM0 and TE0 modes.

[0049] To ensure that the waveguide lengths between the first polarization rotating beam splitter 4 and the first 50 / 50 coupler are the same, a first compensation waveguide 32 is connected between the first polarization control structure 5 and the second polarization control structure 6; to ensure that the waveguide lengths between the second 50 / 50 coupler 20 and the second polarization rotating beam splitter 8 are the same, a second compensation waveguide 33 is connected between the second polarization control structure 6 and the second polarization rotating beam splitter 8.

[0050] Two TE0 mode light fields output from the first polarization rotating beam splitter 4 sequentially enter the first polarization control structure 5, the second polarization control structure 6, and the third polarization control structure 7. Each of these structures uses an electrically controlled phase shifter to generate a phase delay. The phase of the electrically controlled phase shifter has a deterministic functional relationship with the applied voltage, allowing for deterministic control of the phase delay by adjusting the voltage. During polarization control, once the voltage of the electrically controlled phase shifter reaches saturation, it can be adjusted by adding or subtracting V... 2π The voltage resets the electrically controlled phase shifter. Each control structure uses a parallel waveguide electrically controlled phase shifter for phase control and has two control ports, resulting in a total of three pairs and six control ports for the entire silicon-based optoelectronic chip 1. During polarization control, only one of the electrically controlled phase shifters in each pair needs to be used. When it reaches saturation, the other phase shifter in the same control structure can be used, simultaneously resetting the currently saturated electrically controlled phase shifter.

[0051] like Figure 5 As shown, the single-mode fiber, high numerical aperture fiber, and silicon-based optoelectronic chip 1 used in this embodiment are suitable for the 0-band and the C-band communication band. A continuous beam is generated using a 1550nm fiber-pigment DFB laser 38, and the beam intensity is adjusted using a variable optical attenuator 39 to adjust the beam intensity required for the experiment. The beam is split by a 50 / 50 beam splitter 40, with one beam connected to a first power meter 41 to detect the optical power of the input light, and the other beam connected to a manual polarization controller 42 to adjust the polarization state of the input light. Then, the single-mode fiber from the manual polarization controller 42 is converted into a first high numerical aperture fiber 11 through a first fiber connector 13. The first high numerical aperture fiber 11 is then coupled to the first end-face coupling structure 3 at the edge of the silicon-based optoelectronic chip 1, coupling the light into the silicon-based optoelectronic chip 1. Then, the light is output from the second end-face coupling structure 9 through the dynamic polarization control system on the silicon-based optoelectronic chip 1, and then output to the second high numerical aperture fiber 12 through the second end-face coupling structure 9, and finally output to the second fiber connector 14 through the single-mode fiber. This allows the light passing through the silicon-based optoelectronic chip 1 to be output to the polarization beam splitter 43, splitting the light into two paths, one of which is connected to the second power meter 44, and the other is connected to the photodetector 45.

[0052] In the experiment, a 25μm gold wire was used to bond the external PCB circuit board to the pads on the chip. This method applied a driving voltage to the electrically controlled phase shifter on the dynamic polarization controller, changing the phase delay in the phase shifter to ensure normal operation of the polarization controller. The electrically controlled phase shifter was 400μm long and had a resistance of 2KΩ. The output power was changed by altering the voltage across the electrically controlled phase shifter. The expression for converting voltage into power applied to the electrically controlled phase shifter is as follows:

[0053]

[0054] Where R represents the resistance of the electronically controlled phase shifter; P represents the output power of the electronically controlled phase shifter; and V represents the voltage applied to the electronically controlled phase shifter.

[0055] The thermal power and phase shift of the electronically controlled phase shifter have a good linear relationship, enabling precise phase control and accelerating the locking speed of dynamic polarization control. Tests showed that increasing the power of the electronically controlled phase shifter from 0mW to 50mW resulted in a total phase shift of 3π, which, after calculation, corresponds to a voltage increase from 0V to 10V. Figure 6 As shown, the phase change is linearly related to the power ratio, so it is not necessary to use a high voltage greater than 10V for operation.

[0056] In dynamic polarization control, simulated annealing, gradient algorithms, and other dynamic polarization control algorithms are often used to automatically lock the polarization of light. One light path connected to photodetector 45 is used for polarization locking and calculating the extinction ratio. The power of this path changes from maximum to minimum, causing it to change from a light-transmitting state to an extinct state, at which point the power of this path is at its minimum. The voltage collected by photodetector 45 can be received from the USB6259 acquisition card receiver 46 via the computer control terminal 47. Then, the output voltage of the USB6259 acquisition card output terminal 48 is controlled using a simulated annealing algorithm to control the electrically controlled phase shifter on the silicon-based optoelectronic chip 1, locking the light path to its minimum value, achieving the extinction state. The extinction ratio of this light path is then calculated through data processing. One optical path connected to the second power meter 44 is used to calculate the extinction ratio. Before locking, the manual polarization controller 42 is adjusted to minimize the power of this path and make it reach the extinction state. Then, polarization locking is performed. After locking, the power of this end is at its maximum. The maximum and minimum values ​​are read from the second power meter 44 to calculate the extinction ratio of this end.

[0057] Experimental Results: In this experiment, a 1mW laser beam in the 1550nm communication band was coupled into the dynamic polarization controller via a lens and fiber optic cable. Path 1 was connected to the photodetector 35, and path 2 was connected to the second power meter 44. The manual polarization controller 42 was adjusted so that the maximum light transmission of path 1 was approximately 300μW (power decreasing from high to low). The polarization-locked result is as follows. Figure 7 As shown, the locking results indicate that when using a fixed step size of 0.01V, the dynamic polarization controller of this invention can lock the extinction ratio of the light path to above 25dB. The initial extinction ratio of around 12dB in the locking results is due to the saturation of the photodetector at 45°.

[0058] In summary, by coupling light into the silicon-based optoelectronic chip 1 through the end-face coupling structure 3, the loss of light entering the chip from the external high numerical aperture optical fiber is reduced to 2dB. Moreover, after using the polarization rotation beam splitter and locking by this dynamic polarization controller, the dynamic extinction ratio can reach more than 25dB.

[0059] Based on the theoretical analysis and experimental verification above, it is sufficient to prove that this invention has lower coupling loss and a higher polarization extinction ratio compared to existing dynamic polarization controllers based on silicon-based optoelectronic chips. Furthermore, the addition of the first polarization rotating beam splitter 4 better ensures that the light entering this dynamic polarization controller is in TE0 mode. Moreover, the design of the end-face coupling structure with the input and output ends on the same side is more convenient than that of the grating coupling structure in terms of later packaging.

[0060] The foregoing has shown and described the main features and advantages of the present invention. It will be apparent to those skilled in the art that the specific embodiments of the present invention are not limited to the details of the exemplary embodiments described above. Furthermore, without departing from the spirit or essential characteristics of the present invention, the inventive concept and design ideas of the present invention can be implemented in other specific forms, and these should be equivalently included within the protection scope disclosed in the technical solutions of the present invention. Therefore, the embodiments should be considered exemplary and non-limiting in all respects. The scope of the present invention is defined by the appended claims rather than the foregoing description, and thus all changes falling within the meaning and scope of the equivalents of the claims are intended to be included within the present invention.

[0061] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A dynamic polarization controller based on a silicon-based optoelectronic chip, characterized in that: The device includes a silicon-based optoelectronic chip (1), an input / output structure (2) is connected to the side of the silicon-based optoelectronic chip (1), and a first end-face coupling structure (3) connected to the input end of the input / output structure (2) and a second end-face coupling structure (9) connected to the output end of the input / output structure (2) are respectively provided on the silicon-based optoelectronic chip (1). A first polarization rotation beam splitter (4), a first polarization control structure (5), a second polarization control structure (6), a third polarization control structure (7), and a second polarization rotation beam splitter (8) are sequentially connected between the first end-face coupling structure (3) and the second end-face coupling structure (9). The first polarization control structure (5) includes a first electrically controlled phase shifter (15) and a second electrically controlled phase shifter (16), which can realize the 0° polarization control function; the second polarization control structure (6) includes a first 50 / 50 coupler (17), a third electrically controlled phase shifter (18), a fourth electrically controlled phase shifter (19), and a second 50 / 50 coupler (20), which can realize the 45° polarization control function; the third polarization control structure (7) includes a fifth electrically controlled phase shifter (21) and a sixth electrically controlled phase shifter (22), which can realize the 0° polarization control function.

2. A dynamic polarization controller based on a silicon-based optoelectronic chip according to claim 1, characterized in that: The input / output structure (2) includes an array fiber FA port (10), a first fiber connector (13), and a second fiber connector (14). The array fiber FA port (10) includes a first high numerical aperture fiber (11) as the input end and a second high numerical aperture fiber (12) as the output end. One end of the first high numerical aperture fiber (11) is connected to the first end face coupling structure (3), and the other end is connected to the first fiber connector (13) through a single-mode fiber. One end of the second high numerical aperture fiber (12) is connected to the second end face coupling structure (9), and the other end is connected to the second fiber connector (14) through a single-mode fiber.

3. A dynamic polarization controller based on a silicon-based optoelectronic chip according to claim 1, characterized in that: Both the first end-face coupling structure (3) and the second end-face coupling structure (9) are constructed as trapezoidal end-face coupling structures.

4. A dynamic polarization controller based on a silicon-based optoelectronic chip as described in claim 1, characterized in that: The first electronically controlled phase shifter (15) is powered by the first pad (24) and the second pad (25); the second electronically controlled phase shifter (16) is powered by the third pad (23) and the second pad (25), with the second pad (25) being the common terminal; The third electronically controlled phase shifter (18) is powered by the fourth pad (27) and the fifth pad (28); the fourth electronically controlled phase shifter (19) is powered by the sixth pad (26) and the fifth pad (28), with the fifth pad (28) being the common terminal; The fifth electrically controlled phase shifter (21) is powered by the seventh pad (30) and the eighth pad (31); the sixth electrically controlled phase shifter (22) is powered by the ninth pad (29) and the eighth pad (31), with the eighth pad (31) being the common terminal.

5. A dynamic polarization controller based on a silicon-based optoelectronic chip according to claim 1, characterized in that: The first polarization rotating beam splitter (4) is composed of a first polarization rotating part (34) and a first polarization beam splitting part (35); the first polarization rotating part (34) is composed of a first etched waveguide (49) and the front half of a first transition waveguide (50); the first polarization beam splitting part (35) is composed of the rear half of a first transition waveguide (50) and a first thermally insulating waveguide (51); The second polarization rotating beam splitter (8) is composed of a second polarization beam splitting section (36) and a second polarization rotating section (37); the second polarization beam splitting section (36) is composed of the rear half of the second transition waveguide (53) and the second thermally insulating waveguide (54); the second polarization rotating section (37) is composed of the second etched waveguide (52) and the front half of the second transition waveguide (53).

6. A dynamic polarization controller based on a silicon-based optoelectronic chip according to claim 1, characterized in that: A first compensation waveguide (32) is connected between the first polarization control structure (5) and the second polarization control structure (6); a second compensation waveguide (33) is connected between the second polarization control structure (6) and the second polarization rotating beam splitter (8).

7. A control method for a dynamic polarization controller based on a silicon-based optoelectronic chip as described in claim 1, characterized in that: Includes the following steps: Step 1: An arbitrary polarization state optical field in an external single-mode fiber is input to a first high numerical aperture fiber (11) through the first fiber connector (13) in the input-output structure (2) for mode conversion. After mode matching, it is transmitted to the first end-face coupling structure (3), and after further mode conversion, it is transmitted to the first polarization rotating beam splitter (4). The arbitrary polarization state optical field entering the first polarization rotating beam splitter (4) is divided into a TM mode fundamental mode optical field TM0 and a TE mode fundamental mode optical field TE0. The TM0 mode optical field is converted into a higher-order mode optical field TE1 of the TE mode through the first polarization rotating part (34). The E0 mode light field does not change; then the TE1 mode light field and the TE0 mode light field enter the first polarization beam splitter (35). The TE0 mode light field is transmitted along the first transition waveguide (50) without changing mode and is output from the first transition waveguide (50) port of the first polarization rotating beam splitter (4). The TE1 mode light field is coupled from the first transition waveguide (50) to the first adiabatic waveguide (51) and is output from the first adiabatic waveguide (51) port of the first polarization rotating beam splitter (4), and the mode is changed to TE0. The two beams output from the first polarization rotating beam splitter (4) are both in the TE0 mode. Step 2: The two TE0 mode light fields output from the first polarization rotating beam splitter (4) enter the first polarization control structure (5), the second polarization control structure (6) and the third polarization control structure (7) in sequence; the first polarization control structure (5), the second polarization control structure (6) and the third polarization control structure (7) all use electronically controlled phase shifters to generate phase delay; Step 3: After passing through three polarization-locking structures, the two TE0 mode light fields output from the third polarization control structure (7) enter the second polarization rotating beam splitter (8), the light from the sixth electrically controlled phase shifter (22) enters the second transition waveguide (53), and the light from the fifth electrically controlled phase shifter (21) enters the second adiabatic waveguide (54). The TE0 mode light in the second transition waveguide (53) still propagates along the second transition waveguide (53) in the TE0 mode without changing its mode. The TE0 mode light in the second adiabatic waveguide (54) is split in the second polarization beam splitting section. (36) The light is coupled from the second adiabatic waveguide (54) to the second transition waveguide (53) and the mode is converted to TE1 mode. The two beams are combined into one beam and then enter the second polarization rotation part (37). The second polarization rotation part (37) converts the TE1 mode to the TM0 mode. The TE0 mode does not change. Then the light of the two modes, TM0 and TE0, is input into the second end face coupling structure (9). After mode conversion and matching, it is output to the second high numerical aperture fiber (12) in the input-output structure (2). After the mode is converted again, it is output through the second fiber connector (14).

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