A structure and method for non-destructive performance characterization of silicon photonic chips for silicon photonic gyroscopes

Abstract

The present invention provides a non-destructive performance characterization structure of a silicon photonic chip for a silicon photonic gyroscope, comprising an optical engine chip, a coupling optical fiber, a light sensitive chip, a light source, a detector, and a phase modulator; the optical engine chip comprises two gyro couplers, a redundant coupler, and two gratings, the gyro coupler is a Y-type coupler, and the redundant coupler is a 2×2 coupler, which is located between the two gyro couplers; the ports of one gyro coupler are respectively connected to the light source, the detector, and a port of the redundant coupler, the ports of the other gyro coupler are respectively connected to a port of the redundant coupler and two input ports of the phase modulator, and the other two ports of the redundant coupler are respectively connected to the two gratings; the coupling optical fiber comprises two, which are respectively spatially optically coupled with the two gratings; the two output ports of the phase modulator are respectively connected to the input and output ports of the waveguide coil on the light sensitive chip. The present invention adds one redundant coupler and two vertically coupled grating structures to the silicon photonic chip, realizes the independent characterization and testing of the light source, the ring, and the detector on the silicon photonic chip, and solves the non-destructive testing problem of the silicon photonic core.

Description

Technical Field

[0001] The present invention belongs to the technical field of optical gyroscopes, and in particular relates to a lossless performance characterization structure and method of a silicon photonic chip for a silicon photonic gyroscope. Background Art

[0002] Silicon photonic gyroscopes provide new ideas for the integration and miniaturization of fiber gyroscopes: by replacing the discrete optical devices of traditional fiber gyroscopes with silicon-based optical chips, their size, weight, cost and power consumption will be greatly reduced. Silicon photonic gyroscopes have become an important development direction for gyro inertial devices.

[0003] The performance of silicon photonic chips directly determines the performance of silicon photonic gyroscopes. For example, the output optical power of the light source on the chip and the total transmission loss of the waveguide coil determine the gyroscope signal-to-noise ratio, the light source output extinction ratio determines the size of the gyroscope polarization noise, and the detection responsivity of the detector on the chip determines the detection accuracy. Therefore, the performance characterization of silicon photonic chips is a necessary step to achieve iterative optimization. It is necessary not only to accurately test the performance of silicon photonic chips, but also to avoid damaging their structure and causing device failure. Silicon photonic chips use integrated design and processing, and the performance of their various functional components is difficult to characterize and test independently, which has become an important constraint on the performance characterization and improvement of silicon photonic chips. There is an urgent need to find a structure and method that does not damage the device performance and facilitates chip performance testing. Summary of the invention

[0004] In view of the technical problem in the prior art that the performance of silicon photonic chips for silicon photonic gyroscopes is difficult to characterize and test, the present invention provides a lossless performance characterization structure and method for silicon photonic chips for silicon photonic gyroscopes. By adding a redundant test coupler and two vertically coupled grating structures in the silicon photonic chip, independent characterization and testing of the light source, ring and detector on the silicon photonic chip are achieved. This method has the technical advantages of independent testing, simple calculation and precise testing. In addition, the characterization structure does not require optical fiber coupling into the chip, thus avoiding damage to the silicon photonic chip caused by later disassembly, and has lossless characteristics.

[0005] The technical solution adopted by the present invention to solve the above technical problems is as follows:

[0006] A silicon photonic chip lossless performance characterization structure for a silicon photonic gyroscope comprises an optical engine chip, a coupling optical fiber, a light sensitive chip, a light source, a detector, and a phase modulator; the optical engine chip comprises a first gyro coupler, a second gyro coupler, a redundant coupler, a first grating, and a second grating, the first and second gyro couplers are Y-type couplers, and the redundant coupler is a 2×2 coupler located between the first and second gyro couplers; the ports of the first gyro coupler are respectively connected to the light source, the detector, and a port of the redundant coupler, the ports of the second gyro coupler are respectively connected to a port of the redundant coupler and two input ports of a phase modulator, and the other two ports of the redundant coupler are respectively connected to a first grating and a second grating; the coupling optical fiber comprises a first coupling optical fiber and a second coupling optical fiber, and the first and second coupling optical fibers are respectively spatially optically coupled with the first grating and the second grating; the two output ports of the phase modulator are respectively connected to the input port and the output port of the waveguide coil on the light sensitive chip.

[0007] Furthermore, the light source, the detector, and the phase modulator are integrated on the light engine chip;

[0008] The spacing between the redundant coupler and the first and second gyro couplers ranges from 5 to 10 μm;

[0009] The waveguide coil on the photosensitive chip is a square coil with a multi-layer coil structure;

[0010] One end of the first and second coupling optical fibers away from the first and second gratings is used to connect to an auxiliary testing device, and the auxiliary testing device is one of an external light source, an extinction ratio meter, and a power meter.

[0011] Furthermore, the redundant coupler includes a multimode interference zone, an input tapered waveguide, an output tapered waveguide, an input waveguide, and an output waveguide. There are two input tapered waveguides, and both ends of each input tapered waveguide are respectively connected to the multimode interference zone and a section of input waveguide. There are two output tapered waveguides, and both ends of each output tapered waveguide are respectively connected to the multimode interference zone and a section of output waveguide. The redundant coupler has symmetrical structures on both sides of the input and output.

[0012] Furthermore, the first grating and the second grating are fan-shaped gratings with the same structure, which include a fan-shaped grating area, a fan-shaped plane area, and a transition waveguide in sequence. The fan-shaped grating area is used for light alignment and coupling with the optical fiber, the fan-shaped plane area is used for light field expansion, and the transition waveguide is used to connect the grating structure with the redundant coupler to ensure that the optical mode field remains unchanged.

[0013] Furthermore, the mode field diameter of the coupled optical fiber is 5-8μm, the radius R2 of the fan-shaped grating is not less than 30μm, the arc center angle RA is not less than 40°, the waveguide height H2 of the fan-shaped grating area ranges from 50-100nm, the grating size W2 of the fan-shaped grating area is 500nm, the transition waveguide length is more than 500nm, and the transition waveguide width is 200-800nm.

[0014] The present invention also provides a silicon photonic chip for a silicon photonic gyroscope. The silicon photonic gyroscope is a dual-axis or tri-axis gyroscope. The silicon photonic chip includes two or three waveguide optical paths. Each waveguide optical path adopts the lossless performance characterization structure of the silicon photonic chip for the silicon photonic gyroscope to perform performance characterization.

[0015] The present invention also provides a method for designing a redundant coupler for a silicon photonic chip lossless performance characterization structure for a silicon photonic gyroscope, comprising the following steps:

[0016] S10, calculating the theoretical length range of the multi-mode interference region;

[0017] S20, setting the transmission light wavelength and the width of the multimode interference zone, modeling the waveguide transmission light field, simulating the relationship between the length of the multimode interference zone and the output optical power, and taking the length of the multimode interference zone corresponding to the extreme value of the output optical power as the length of the multimode interference zone;

[0018] S30, simulating the maximum widths of the input and output tapered waveguides to obtain the relationship between the maximum widths of the input and output tapered waveguides and the output optical power, and taking the maximum width of the tapered waveguide corresponding to the extreme value of the output optical power as the maximum width of the input and output tapered waveguides;

[0019] S40, simulating the relationship between the output tapered waveguide spacing and the output optical power according to the maximum width of the output tapered waveguide, and taking the output tapered waveguide spacing corresponding to the output optical power extreme value as the output tapered waveguide spacing;

[0020] S50, simulating the input and output tapered waveguide lengths to obtain the relationship between the input and output tapered waveguide lengths and the output optical power, and taking the tapered waveguide length corresponding to the extreme value of the output optical power as the input and output tapered waveguide lengths.

[0021] The present invention also provides a method for lossless performance characterization of a silicon photonic chip for a silicon photonic gyroscope, which uses the aforementioned lossless performance characterization structure to characterize the optical power and extinction ratio of a light source, comprising the following steps:

[0022] S101, placing the silicon photonic chip on a fixture, assembling one end of the second coupling optical fiber on the rotating mechanism of the adjustment frame, and connecting the other end to an optical power meter;

[0023] S102, controlling the movement of the second coupling optical fiber by adjusting the frame so that the second coupling optical fiber maintains a certain distance from the second grating, thereby achieving initial alignment of the spatial optical path;

[0024] S103, controlling the light source of the silicon photonic chip to output a constant current at a constant temperature;

[0025] S104, controlling the movement of the second coupling optical fiber by adjusting the frame, monitoring the optical power output by the optical power meter, and achieving fine alignment when the optical power reaches the maximum value, and recording the optical power value at this time;

[0026] S105, replacing the optical power meter connected to the second coupling optical fiber with an extinction ratio meter;

[0027] S106, controlling the rotation mechanism of the adjustment frame to rotate, monitoring the extinction ratio output by the extinction ratio meter, achieving angle alignment when the extinction ratio reaches a maximum value, and recording the extinction ratio value at this time.

[0028] The present invention also provides a method for non-destructive performance characterization of a silicon photonic chip for a silicon photonic gyroscope, which uses the aforementioned non-destructive performance characterization structure to characterize the detector responsivity, comprising the following steps:

[0029] S201, placing the silicon photonic chip on a fixture, assembling one end of the second coupling optical fiber on the rotating mechanism of the adjustment frame, and connecting the other end to an optical power meter;

[0030] S202, controlling the movement of the second coupling optical fiber by adjusting the frame so that the second coupling optical fiber maintains a certain distance from the second grating, thereby achieving initial alignment of the spatial optical path;

[0031] S203, controlling the light source of the silicon photonic chip to output a constant current at a constant temperature;

[0032] S204, controlling the movement of the second coupling optical fiber by adjusting the frame, monitoring the optical power output by the optical power meter, and when the optical power reaches the maximum value, performing fine alignment, and recording the optical power value at this time;

[0033] S205, replacing the optical power meter connected to the second coupling optical fiber with an external light source, and controlling the external light source to work;

[0034] S206, assembling one end of the first coupling optical fiber on the rotating mechanism of the adjustment frame, connecting the other end to the optical power meter, controlling the adjustment frame to adjust the relative distance between the first coupling optical fiber and the first grating, adjusting to the maximum optical power output by the optical power meter, and recording the optical power P outputted stably by the optical power meter in ;

[0035] S207, supplying power to the detector of the silicon photonic chip, collecting the detector output voltage V, and calculating the detector responsivity of the silicon photonic chip. The detector responsivity calculation method is:

[0036] A in =P in V / 2R f

[0037] Among them, R f is the transimpedance of the detector.

[0038] The present invention also provides a method for lossless performance characterization of a silicon photonic chip for a silicon photonic gyroscope, which uses the aforementioned lossless performance characterization structure to characterize coil loss, comprising the following steps:

[0039] S301, using the aforementioned non-destructive performance characterization structure to characterize the detector responsivity method to obtain the detector responsivity A in ;

[0040] S302: The second coupling optical fiber connected to the second grating is connected to an external light source, and the emitted power is P in of light;

[0041] S303: The first coupling optical fiber connected to the first grating is connected to an optical power meter, the silicon photonic chip light source stops working, and the test optical power is P out ;

[0042] S304, calculating the loss of the redundant coupler:

[0043] LOSS 冗余 =-10log(P out / P in )-3dB

[0044] S305: The first coupling optical fiber connected to the first grating is connected to an external light source, and the emitted power is P' in The light from the second grating stops working;

[0045] S306, collecting the output voltage V' of the silicon photonic chip detector, and calculating the total loss of the silicon photonic chip as:

[0046] LOSS 总 =-10log(2V' / A in R f P' in )

[0047] Among them, R f is the transimpedance of the detector;

[0048] S306. Calculate the loss of the coil as:

[0049] LOSS 线圈 =LOSS 总 -LOSS 冗余 -LOSS Y波导 -6dB

[0050] Among them, LOSS Y波导 is the insertion loss of the Y-waveguide phase modulator.

[0051] The beneficial effects of the present invention compared with the prior art are as follows:

[0052] The present invention provides a lossless performance characterization structure of a silicon photonic chip for a silicon photonic gyroscope, which takes into account the realization of both optical engine chip characterization and photosensitive chip characterization. According to different functional components, the optical engine chip is further subdivided into light source characterization and detector characterization. The light source characterization mainly tests the optical power and extinction ratio parameters of the silicon photonic chip, the detector characterization mainly tests the responsivity parameters of the silicon photonic chip, and the photosensitive chip characterization mainly tests the loss parameters of the waveguide coil. The characterization structure described in the present invention is used to realize independent characterization and testing of the light source, ring and detector on the silicon photonic chip, which has the technical advantages of independent testing, simple calculation and precise testing. In addition, the characterization structure does not need to couple the optical fiber into the chip, which avoids the damage of the silicon photonic chip introduced by the later disassembly, and has the lossless characteristics.

[0053] The lossless performance characterization structure of the silicon photonic chip for the silicon photonic gyroscope of the present invention is simple, and only one redundant test coupler and two vertical coupling grating coupling structures are added to the waveguide optical path. The preparation process is simple, the technology is mature, and the characterization cost is low.

[0054] The present invention provides a method for non-destructive performance characterization of a silicon photonic chip for a silicon photonic gyroscope, which has a simple principle, is easy to implement and has high test accuracy. BRIEF DESCRIPTION OF THE DRAWINGS

[0055] The included drawings are used to provide a further understanding of the embodiments of the present invention, which constitute a part of the specification, are used to illustrate the embodiments of the present invention, and together with the text description, explain the principles of the present invention. Obviously, the drawings in the following description are only some embodiments of the present invention, and for ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0056] Figure 1 A schematic diagram of a structure for characterizing the lossless performance of a silicon photonic chip provided in a specific embodiment of the present invention;

[0057] Figure 2 A schematic diagram of the structure of a redundant coupler provided in a specific embodiment of the present invention;

[0058] Figure 3 A simulation curve of multimode interference region length and output optical power provided by a specific embodiment of the present invention;

[0059] Figure 4 A simulation curve of the relationship between the maximum width of the tapered waveguide and the output optical power provided by a specific embodiment of the present invention;

[0060] Figure 5 A simulation curve of the relationship between the output tapered waveguide spacing and the output optical power provided by a specific embodiment of the present invention;

[0061] Figure 6 A simulation curve of the relationship between the tapered waveguide length and the output optical power provided in a specific embodiment of the present invention;

[0062] Figure 7 Schematic diagram of a grating structure provided by a specific embodiment of the present invention, (a) schematic diagram of coupling between a grating structure and a coupling optical fiber, (b) schematic diagram of a grating structure;

[0063] Figure 8 Flow chart of the non-destructive performance characterization method of silicon photonic chips provided for a specific embodiment of the present invention; (a) schematic diagram of the performance characterization of an optical engine chip (b) schematic diagram of the performance characterization of a photosensitizer chip.

[0064] The above drawings include the following reference numerals:

[0065] 1. Optical engine chip; 101. Light source; 102. Detector; 103. First gyro coupler; 104. Second gyro coupler; 105. Redundant coupler; 106. First grating; 107. Second grating; 108. Phase modulator; 2. Coupling optical fiber; 3. Photosensitive chip. DETAILED DESCRIPTION

[0066] Specific embodiments of the present invention are described in detail below. In the following description, for the purpose of explanation and not limitation, specific details are set forth to help fully understand the present invention. However, it will be apparent to those skilled in the art that the present invention may also be practiced in other embodiments that depart from these specific details.

[0067] It should be noted that in order to avoid obscuring the present invention due to unnecessary details, only the device structure and / or processing steps closely related to the scheme of the present invention are shown in the drawings, while other details that are not closely related to the present invention are omitted.

[0068] As another aspect of the present invention, taking a silicon-based optical engine chip integrating a light source, a detector, and a phase modulator as an example, a lossless performance characterization structure of a silicon photonic chip for a silicon photonic gyroscope is provided, such as Figure 1 As shown, it mainly includes a silicon-based optical engine chip 1, a coupling optical fiber 2, and a silicon-based photosensitive chip 3.

[0069] The silicon-based optical engine chip 1 mainly realizes the functions of light emission, light splitting and detection, and integrates a light source 101, a detector 102, a first gyro coupler 103, a second gyro coupler 104, a redundant coupler 105, a first grating 106, a second grating 107, and a phase modulator 108. The first gyro coupler 103 and the second gyro coupler 104 are Y-type couplers, including three ports, two input ports of the first gyro coupler 103 are respectively connected to the light source 101 and the detector 102, one output port is connected to an input port of the redundant coupler 105, one input port of the second gyro coupler 104 is connected to an output port of the redundant coupler 105, and two output ports are respectively connected to two input ports of the phase modulator 108; the redundant coupler 105 is located between the first and second gyro couplers, and the redundant coupler 105 is a 2×2 coupler, such as Figure 1 As shown, there are two input ports a and b, and two output ports c and d. The input port a is connected to the first grating 106, the input port b is connected to an output port of the first gyro coupler 103, the output port c is connected to the second grating 107, and the output port d is connected to an input port of the second gyro coupler 104. The first grating 106 and the second grating 107 are respectively used for spatial optical coupling with the coupling optical fiber. The two output ports of the phase modulator 108 are respectively connected to the input and output ports of the waveguide coil on the silicon-based photosensitive chip 3. Considering the size and loss performance of the optical engine chip 1, the spacing between the redundant coupler and the first and second gyro couplers is controlled to be 5-10μm.

[0070] The coupling optical fiber 2 is used to guide the light from the external light source into the silicon-based light engine chip 1 or to guide the light inside the silicon-based light engine chip 1 to an external testing device. One end of the coupling optical fiber 2 establishes spatial optical coupling with the first grating and the second grating through a clamping device and an adjustment frame to achieve lossless light transmission, and the other end is connected to an external light source, a power meter, an extinction ratio meter and other auxiliary testing devices.

[0071] The silicon-based photosensitive chip 3 integrates a spiral on-chip waveguide coil for sensing the Sagnac phase shift introduced by the external rotation speed change. The silicon-based photosensitive chip 3 mainly includes a waveguide coil, which can adopt a single-layer or multi-layer coil structure. At the same time, the waveguide coil can be designed as a circular coil or a square coil. The key parameters of the optical waveguide coil, such as the number of windings, the number of stacking layers, and the winding shape, can be optimized and determined according to the size and performance of the optical fiber gyroscope. Preferably, the waveguide coil is a square coil with a multi-layer coil structure to improve space utilization and reduce chip size.

[0072] The structure and method for lossless performance characterization of silicon photonic chips based on the combination of redundant couplers and gratings described in the present invention are not only applicable to single-axis silicon photonic gyroscopes, but also to dual-axis and tri-axis silicon photonic gyroscopes, and have good scalability. For dual-axis and tri-axis silicon photonic gyroscopes, a redundant coupler and two gratings are independently integrated between two gyro couplers in the waveguide optical path corresponding to each axis of the silicon-based optical engine chip 1, and lossless performance characterization of silicon photonic chips can also be achieved.

[0073] It should be noted that, in the present embodiment, the light source and the detector may be directly integrated on the silicon-based optical engine chip to carry out lossless performance characterization of the silicon photonic chip for the silicon photonic gyroscope. In other types of silicon photonic chips, the light source and the detector may not be integrated on the silicon-based optical engine chip, but may be designed on the substrate. By adopting the method of integrating redundant couplers and gratings as described in the present invention, lossless performance characterization of the silicon photonic chip for the silicon photonic gyroscope may also be achieved.

[0074] As another aspect of the present invention, a method for designing a lossless performance characterization structure of a silicon photonic chip for a silicon photonic gyroscope is provided, which specifically comprises the following steps:

[0075] S1. Design of redundant coupler structure parameters

[0076] Redundant coupler structure Figure 2 As shown, it includes a multimode interference region, an input tapered waveguide, an output tapered waveguide, an input waveguide, and an output waveguide. There are two input tapered waveguides, and the two ends of each input tapered waveguide are respectively connected to the multimode interference region and a section of input waveguide. There are two output tapered waveguides, and the two ends of each output tapered waveguide are respectively connected to the multimode interference region and a section of output waveguide. Specifically, the input waveguide and the input tapered waveguide are connected end to end, and the output waveguide and the output tapered waveguide are connected end to end. The multimode interference region is composed of input tapered waveguides a and b to form an input port, and the output tapered waveguides c and d to form an output port. The redundant coupler has symmetrical structures on both sides of the input and output. The redundant coupler 105 input and output ports are reciprocal in design, that is, the input and output ports a, b, c, d of the redundant coupler 105 have the same waveguide parameters and can be used interchangeably.

[0077] The parameters for designing redundant couplers include: the input waveguide length is L i , the input waveguide widths are W ia , W ib , the input tapered waveguide length is L it , the maximum width is W it , the length of the multimode interference zone is L m , width is W m , the length of the output tapered waveguide is L ot , the maximum width is W ot , the output waveguide length is L o, width respectively W oc and W od , the spacing between the two input or output tapered waveguides is W o .

[0078] The redundant coupler structural parameter design process is as follows:

[0079] (1) Calculate the theoretical length range of the multimode interference zone

[0080] The theoretical length of the multimode interference region is determined by the following formula:

[0081]

[0082] Wherein, M and N are the input and output waveguide numbers, and Δβ is the propagation constant difference between different modes in the waveguide. In this embodiment, M and N are both 2. Δβ is a range of values, which is determined according to the material parameters of the multimode interference region.

[0083] The theoretical length of the multimode interference region is obtained from formula (1), while the actual waveguide parameters still need to be simulated and verified by establishing a light field model to further optimize the device parameters.

[0084] (2) Set the wavelength of light to 1310 nm and determine the width of the multimode interference region as W based on empirical values. m The three-dimensional finite time-domain difference method (FDTD) is used to model the waveguide transmission light field, and the relationship between the length of the multimode interference zone and the output optical power is obtained by simulation, such as Figure 3 As shown, the interference zone length corresponding to the extreme value of the output optical power is taken, and is accurate to one decimal place (in μm) as the multi-mode interference zone length.

[0085] (3) Input and output tapered waveguide width W it , W ot By simulation, the relationship between the input and output tapered waveguide widths and the output optical power is obtained, such as Figure 4 As shown, the tapered waveguide width corresponding to the extreme value of the output optical power is taken, and is accurate to one decimal place (in μm) as the tapered waveguide width;

[0086] (4) According to the maximum width of the input and output tapered waveguides, the spacing W of the redundant coupler output tapered waveguides is o Scan and simulate to obtain the relationship between the output tapered waveguide spacing and the output optical power, such as Figure 5 As shown, the output tapered waveguide spacing corresponding to the output optical power extreme value is taken, and is accurate to one decimal place (in μm) as the output tapered waveguide spacing;

[0087] (5) Input and output tapered waveguide length L it , L otFor simulation, the relationship between the input and output tapered waveguide lengths and the output optical power is obtained, such as Figure 6 As shown, the tapered waveguide length corresponding to the extreme value of the output optical power is taken, and is accurate to one decimal place (in μm) as the tapered waveguide length;

[0088] (6) According to the values ​​in steps (2)-(5), the redundant coupler structure design optimization is completed.

[0089] S2. Grating structure parameter design

[0090] like Figure 7 As shown, the grating structure is a fan-shaped structure, which includes a fan-shaped grating area, a fan-shaped plane area, and a transition waveguide in sequence. The fan-shaped grating area is used for light alignment and coupling with the optical fiber, the fan-shaped plane area is used for beam expansion of the light field, and the transition waveguide is used to connect the grating structure with the redundant coupler to ensure that the optical mode field remains unchanged. The key parameters of the grating structure include: the radius R2 of the grating structure, the arc center angle RA, the radius R1 of the fan-shaped plane area, the radius (R2-R1) of the fan-shaped grating area, the base height H1 of the fan-shaped grating area, the waveguide height H2, the grating size W2, and the transition waveguide length and width.

[0091] Preferably, the mode field diameter of the coupled optical fiber is 5-8μm, the radius R2 of the fan-shaped grating is not less than 30μm, and the arc center angle RA is not less than 40°. In order to simplify the calculation and processing difficulty, the radius R1 of the fan-shaped plane area is set to 15μm, and the radius R2-R1 of the fan-shaped grating area is set to 15μm. Considering the silicon-based standard processing technology, the substrate height H1 of the fan-shaped grating area is set to 220nm, the waveguide height H2 of the fan-shaped grating area is in the range of 50-100nm, the grating size W2 of the fan-shaped grating area is 500nm, the transition waveguide length is more than 500nm, and the transition waveguide width is 200-800nm.

[0092] Taking a 1310nm light source and a coupled fiber with a mode field diameter of 5μm as an example, the grating structure parameters are designed as follows:

[0093] (1) Grating structure design: The mode field diameter (MFD) of the coupled fiber is designed to be 5 μm. The fan-shaped grating area adopts a silicon-on-insulator (SOI) processing technology with a substrate height H1 of 220 nm. According to the mode field diameter of the coupled fiber, the simulation obtains that the minimum value of the grating radius (R2-R1) is 15 μm and the maximum value is 30 μm. In this embodiment, R2-R1=15 μm is designed. According to the mode field matching simulation, it is determined that the grating covers at least a 40-degree arc RA=40°; the radius of the fan-shaped plane area is reasonably designed according to the size of the silicon-based optical engine chip. The preferred R1 value range is 10-15 μm. In this embodiment, R1 is 15 μm.

[0094] (2) Design of transition waveguide structure: In order to ensure that the light in the grating enters the a-port of the redundant coupler without changing the mode field, a transition waveguide of more than 500 nm must be retained at the tail end of the fan-shaped structure. In the present invention, the length L of the transition waveguide is designed to be 600 nm, and the width is consistent with the input and output waveguide widths of the redundant coupler, so as to achieve the lowest possible coupling loss on the basis of connecting the optical waveguide to the silicon-based optical engine chip. According to simulation, the width of this part of the transition waveguide is generally 200 to 800 nm, and is designed to be 450 nm in this embodiment.

[0095] (3) Structural design of the fan-shaped grating area: a ridge-type optical waveguide structure is adopted, the substrate height H1 is 220nm, and the silicon-on-insulator (SOI) processing technology is adopted. The waveguide height H2 is 50-100nm, and is designed to be 70nm in this embodiment. The gate size W2 is usually close to the transition waveguide width. According to the simulation of the lowest possible coupling loss, the gate size of the present invention is designed to be 500nm.

[0096] The design dimensions of the above parameters have a processing tolerance of ±10nm to ensure the processing consistency of the fan-shaped optical waveguide spacing.

[0097] As another aspect of the present invention, a method for non-destructive performance characterization of a silicon photonic chip for a silicon photonic gyroscope is provided. Figure 5 As shown, it specifically includes two parts: optical engine chip characterization and photosensor chip characterization. According to different functional components, the optical engine chip is further subdivided into light source characterization and detector characterization. The light source characterization mainly tests the optical power and extinction ratio parameters of the silicon photonic chip, the detector characterization mainly tests the responsivity parameters of the silicon photonic chip, and the photosensitive chip characterization mainly tests the loss parameters of the waveguide coil.

[0098] The method for characterizing the optical power and extinction ratio of a light source based on the lossless performance characterization structure of a silicon photonic chip for a silicon photonic gyroscope specifically includes the following steps:

[0099] (1) Place the silicon photonic chip and the coupling optical fiber on the fixtures respectively. The fixture holding one end of the coupling optical fiber is assembled on the rotating mechanism of the adjustment frame. The other end of the coupling optical fiber is connected to the optical power meter.

[0100] (2) adjusting the relative distance between the coupling optical fiber and the second grating on the silicon photonic chip by means of an adjustment frame to achieve initial alignment; the adjustment frame is used to achieve adjustment in the X, Y, and Z directions, where the X, Y, and Z directions are the three orthogonal directions of the north, east, and east of the geographic coordinate system;

[0101] (3) Using a light source temperature driving module to achieve constant current and constant temperature control of the light source part on the silicon-based light engine chip;

[0102] (4) Finely adjust the adjustment frame in the X, Y, and Z directions until the optical power meter measures the highest optical power, thereby achieving fine alignment. Record the optical power value tested at this time, which is the optical power parameter of the light source;

[0103] (5) The optical power meter is replaced with an extinction ratio meter;

[0104] (6) The rotating mechanism of the adjustment frame is slightly rotated clockwise or counterclockwise with an accuracy of not less than 5 arc seconds. During this process, the relative position of the adjustment frame is kept unchanged. At this time, the coupled optical fiber rotates clockwise or counterclockwise. At the same time, the reading on the extinction ratio meter is observed. The angle is repeatedly fine-tuned until the extinction ratio measured by the extinction ratio meter is the highest, thus achieving angle alignment. The test extinction ratio value at this time is recorded, which is the extinction ratio parameter of the light source.

[0105] Furthermore, the adjustment frame is a conventional device in the field, and the adjustment frame includes adjustment brackets and a rotating mechanism in the X, Y, and Z directions. The rotating mechanism is located at the center of the three adjustment brackets, and the coupled optical fiber is assembled at the center of the rotating mechanism and rotates clockwise or counterclockwise synchronously with the rotating mechanism.

[0106] The detector responsivity characterization method based on the non-destructive performance characterization structure of silicon photonic chip for silicon photonic gyroscope has the following specific steps:

[0107] (1)-(4) are the same as the first four steps of the light source optical power test;

[0108] (5) Replace the optical power meter connected to the coupling optical fiber with an external light source, turn off the light source of the silicon photonic chip, and turn on the external light source;

[0109] (6) Take the second section of coupling fiber and place it on the adjustment frame. Connect the optical power meter to the second section of coupling fiber. Adjust the relative distance between the second section of coupling fiber and the first grating to the maximum optical power until the optical power meter outputs a stable optical power of P. in Due to the port reciprocity of the redundant coupler, the optical power detected at port b should be the same, also P in ;

[0110] (7) The detector of the silicon photonic chip is powered, and the detector output voltage is detected to be V. The calculation method of the detector responsivity of the silicon photonic chip to be tested is:

[0111] A in =P in V / 2R f (2)

[0112] Among them, R f is the transimpedance of the detector.

[0113] The coil loss characterization method based on the lossless performance characterization structure of silicon photonic chip for silicon photonic gyroscope has the following specific steps:

[0114] (1) Obtain the detector responsivity A according to the detector responsivity characterization steps in ;

[0115] (2) A section of coupling fiber connected to the second grating is connected to an external light source, which emits a power of P in of light;

[0116] (3) The other coupling optical fiber connected to the first grating is connected to an external optical power meter. The silicon photonic chip light source does not work. The test optical power is P out ;

[0117] (4) Calculate the loss of the redundant coupler according to the following formula:

[0118] LOSS 冗余 =-10log(P out / P in )-3dB (3)

[0119] (5) The coupling fiber connected to the first grating is connected to an external light source, and the emitted power is P' in The light from the second grating stops working;

[0120] (6) Record the detection voltage of the silicon photonic chip detector as V', and calculate the total loss according to the following formula (the total loss includes the redundant coupler, Y-waveguide phase modulator and coil loss):

[0121] LOSS 总 =-10log(2V' / A in R f P' in ) (4)

[0122] (7) Calculate the coil loss according to the following formula:

[0123] LOSS 线圈 =LOSS 总 -LOSS 冗余 -LOSS Y波导 -6dB (5)

[0124] Among them, LOSS Y波导 is the insertion loss of the Y-waveguide phase modulator, which is 2.7 dB in this embodiment.

[0125] Features described and / or illustrated above for one embodiment may be used in the same or similar manner in one or more other embodiments, and / or combined with or used in place of features in other embodiments.

[0126] It should be emphasized that the term "include / comprises" when used herein refers to the presence of features, integers, steps or components, but does not exclude the presence or addition of one or more other features, integers, steps, components or combinations thereof.

[0127] The many features and advantages of these embodiments are apparent from this detailed description, and thus the appended claims are intended to cover all such features and advantages of these embodiments that fall within their true spirit and scope. Furthermore, since numerous modifications and changes will readily occur to those skilled in the art, it is not intended that the embodiments of the invention be limited to the exact construction and operation illustrated and described, but rather all suitable modifications and equivalents falling within the scope thereof are intended to be covered.

[0128] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

[0129] Parts of the present invention that are not described in detail are well known to those skilled in the art.

Claims

1. A lossless performance characterization structure of a silicon photonic chip for a silicon photonic gyroscope, characterized in that: The invention comprises an optical engine chip, a coupling optical fiber, a photosensor chip, a light source, a detector, and a phase modulator; the optical engine chip comprises a first gyro coupler, a second gyro coupler, a redundant coupler, a first grating, and a second grating, the first and second gyro couplers are Y-type couplers, and the redundant coupler is a 2×2 coupler located between the first and second gyro couplers; the ports of the first gyro coupler are respectively connected to the light source, the detector, and a port of the redundant coupler, the ports of the second gyro coupler are respectively connected to a port of the redundant coupler and two input ports of the phase modulator, and the other two ports of the redundant coupler are respectively connected to the first grating and the second grating; the coupling optical fiber comprises a first coupling optical fiber and a second coupling optical fiber, and the first and second coupling optical fibers are respectively spatially optically coupled with the first grating and the second grating; the two output ports of the phase modulator are respectively connected to the input port and the output port of the waveguide coil on the photosensor chip.

2. The lossless performance characterization structure of silicon photonic chip for silicon photonic gyroscope according to claim 1, characterized in that: The light source, detector, and phase modulator are integrated on the light engine chip; The spacing between the redundant coupler and the first and second gyro couplers ranges from 5 to 10 μm; The waveguide coil on the photosensitive chip is a square coil with a multi-layer coil structure; One end of the first and second coupling optical fibers away from the first and second gratings is used to connect to an auxiliary testing device, and the auxiliary testing device is one of an external light source, an extinction ratio meter, and a power meter.

3. The lossless performance characterization structure of silicon photonic chip for silicon photonic gyroscope according to claim 1, characterized in that: The redundant coupler comprises a multimode interference region, an input tapered waveguide, an output tapered waveguide, an input waveguide, and an output waveguide. There are two input tapered waveguides, and both ends of each input tapered waveguide are respectively connected to the multimode interference region and a section of input waveguide. There are two output tapered waveguides, and both ends of each output tapered waveguide are respectively connected to the multimode interference region and a section of output waveguide. The redundant coupler has symmetrical structures on both sides of input and output.

4. The lossless performance characterization structure of silicon photonic chip for silicon photonic gyroscope according to claim 1, characterized in that: The first grating and the second grating are fan-shaped gratings with the same structure, which include a fan-shaped grating area, a fan-shaped plane area, and a transition waveguide in sequence. The fan-shaped grating area is used for light alignment and coupling with the optical fiber, the fan-shaped plane area is used for light field expansion, and the transition waveguide is used to connect the grating structure with the redundant coupler to ensure that the optical mode field remains unchanged.

5. The lossless performance characterization structure of silicon photonic chip for silicon photonic gyroscope according to claim 4, characterized in that: The mode field diameter of the coupled optical fiber is 5-8μm, the radius R2 of the fan-shaped grating is not less than 30μm, the arc center angle RA of the fan-shaped grating is not less than 40°, the waveguide height H2 of the fan-shaped grating area ranges from 50-100nm, the grating size W2 of the fan-shaped grating area is 500nm, the transition waveguide length is more than 500nm, and the transition waveguide width is 200-800nm.

6. A silicon photonic chip for a silicon photonic gyroscope, characterized in that: The silicon photonic gyroscope is a dual-axis or tri-axis gyroscope, and the silicon photonic chip includes two or three waveguide optical paths, each of which adopts the lossless performance characterization structure of the silicon photonic chip for the silicon photonic gyroscope according to any one of claims 1 to 5 for performance characterization.

7. A redundant coupler design method, characterized in that: The redundant coupler is the redundant coupler according to claim 3, and the design method comprises the following steps: S10, calculating the theoretical length range of the multi-mode interference region; S20, setting the transmission light wavelength and the width of the multimode interference zone, modeling the waveguide transmission light field, simulating the relationship between the length of the multimode interference zone and the output optical power, and taking the length of the multimode interference zone corresponding to the extreme value of the output optical power as the length of the multimode interference zone; S30, simulating the maximum widths of the input and output tapered waveguides to obtain the relationship between the maximum widths of the input and output tapered waveguides and the output optical power, and taking the maximum width of the tapered waveguide corresponding to the extreme value of the output optical power as the maximum width of the input and output tapered waveguides; S40, simulating the relationship between the output tapered waveguide spacing and the output optical power according to the maximum width of the output tapered waveguide, and taking the output tapered waveguide spacing corresponding to the output optical power extreme value as the output tapered waveguide spacing; S50, simulating the input and output tapered waveguide lengths to obtain the relationship between the input and output tapered waveguide lengths and the output optical power, and taking the tapered waveguide length corresponding to the extreme value of the output optical power as the input and output tapered waveguide lengths.

8. A method for non-destructive performance characterization of silicon photonic chips for silicon photonic gyroscopes, characterized in that: The method of using the lossless performance characterization structure of silicon photonic chip for silicon photonic gyroscope according to any one of claims 1 to 5 to characterize the optical power and extinction ratio of the light source comprises the following steps: S101, placing the silicon photonic chip on a fixture, assembling one end of the second coupling optical fiber on the rotating mechanism of the adjustment frame, and connecting the other end to an optical power meter; S102, controlling the movement of the second coupling optical fiber by adjusting the frame so that the second coupling optical fiber maintains a certain distance from the second grating, thereby achieving initial alignment of the spatial optical path; S103, controlling the light source of the silicon photonic chip to output a constant current at a constant temperature; S104, controlling the movement of the second coupling optical fiber by adjusting the frame, monitoring the optical power output by the optical power meter, and achieving fine alignment when the optical power reaches the maximum value, and recording the optical power value at this time; S105, replacing the optical power meter connected to the second coupling optical fiber with an extinction ratio meter; S106, controlling the rotation mechanism of the adjustment frame to rotate, monitoring the extinction ratio output by the extinction ratio meter, achieving angle alignment when the extinction ratio reaches a maximum value, and recording the extinction ratio value at this time.

9. A method for non-destructive performance characterization of silicon photonic chips for silicon photonic gyroscopes, characterized in that: The method of characterizing the detector responsivity by using the non-destructive performance characterization structure of the silicon photonic chip for the silicon photonic gyroscope according to any one of claims 1 to 5 comprises the following steps: S201, placing the silicon photonic chip on a fixture, assembling one end of the second coupling optical fiber on the rotating mechanism of the adjustment frame, and connecting the other end to an optical power meter; S202, controlling the movement of the second coupling optical fiber by adjusting the frame so that the second coupling optical fiber maintains a certain distance from the second grating, thereby achieving initial alignment of the spatial optical path; S203, controlling the light source of the silicon photonic chip to output a constant current at a constant temperature; S204, controlling the movement of the second coupling optical fiber by adjusting the frame, monitoring the optical power output by the optical power meter, and when the optical power reaches the maximum value, performing fine alignment, and recording the optical power value at this time; S205, replacing the optical power meter connected to the second coupling optical fiber with an external light source, and controlling the external light source to work; S206, assembling one end of the first coupling optical fiber on the rotating mechanism of the adjustment frame, connecting the other end to the optical power meter, controlling the adjustment frame to adjust the relative distance between the first coupling optical fiber and the first grating, adjusting to the maximum optical power output by the optical power meter, and recording the optical power P outputted stably by the optical power meter in ; S207, supplying power to the detector of the silicon photonic chip, collecting the detector output voltage V, and calculating the detector responsivity of the silicon photonic chip. The detector responsivity calculation method is: A in =P in V / 2R f Among them, R f is the transimpedance of the detector.

10. A method for non-destructive performance characterization of silicon photonic chips for silicon photonic gyroscopes, characterized in that: The method of characterizing the coil loss by using the lossless performance characterization structure of silicon photonic chip for silicon photonic gyroscope according to any one of claims 1 to 5 comprises the following steps: S301. Obtain the detector responsivity A using the method described in claim 9. in ; S302: The second coupling optical fiber connected to the second grating is connected to an external light source, and the emitted power is P in of light; S303: The first coupling optical fiber connected to the first grating is connected to an optical power meter, and the test optical power is P out ; S304, calculating the loss of the redundant coupler: LOSS 冗余 =-10log(P out / P in )-3dB S305: The first coupling optical fiber connected to the first grating is connected to an external light source, and the emitted power is P' in of light; S306, collecting the output voltage V' of the silicon photonic chip detector, and calculating the total loss of the silicon photonic chip as: LOSS 总 =-10log(2V’ / A in R f P’ in ) Among them, R f is the transimpedance of the detector; S306. Calculate the loss of the coil as: LOSS 线圈 =LOSS 总 -LOSS 冗余 -LOSS Y波导 -6dB Among them, LOSS Y波导 is the insertion loss of the Y-waveguide phase modulator.

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