End face coupler testing device and method, and test array

Abstract

The present invention provides an end face coupler testing device and method, and a test array. The end face coupler testing device is arranged on an optical chip and comprises: a loopback structure, used for being coupled with an external optical fiber array; a cascade test structure, used for testing the on-chip mode field conversion losses of the TE polarized light and the TM polarized light; a polarization splitting module, connected to the cascade test structure and used for inputting the TE polarized light and the TM polarized light into the cascade test structure for testing, and then outputting same; a TE grating coupling module, connected to an input end and an output end of the polarization splitting module and used for inputting the TE polarized light into the cascade test structure and outputting same; and a TM grating coupling module, connected to the input end and the output end of the polarization splitting module and used for inputting the TM polarized light into the cascade test structure and outputting same. According to the present invention, the coupling losses of the TE polarized light and the TM polarized light can be respectively tested, so that the space in chips is saved, and the utilization efficiency of the chips is improved.

Description

End coupler test device, method and test array

[0001] Cross-references

[0002] This application claims priority to Chinese application No. 2023106103903, filed on May 26, 2023. The contents of the above application are incorporated herein by reference. Technical Field

[0003] The present invention relates to the technical field of optical technology, and in particular to an end face coupler testing device, method and test array. Background Art

[0004] Edge couplers (ECs) are used to couple light into (or out of) photonic integrated circuits (PICs). They offer low coupling loss, a wide operating wavelength range, and the ability to carry both TE and TM polarization states. ECs are often coupled to external optical fibers (or fiber arrays); to achieve optimal coupling, the mode field at the EC end face must match the fiber's mode field. Within an optical chip, the mode field of a conventional waveguide is relatively small, while the mode field of an optical fiber is relatively large. Therefore, a transition region (e.g., a wedge-shaped structure) is required within the chip to achieve the transition from small to large mode field sizes. Therefore, EC coupling loss consists of two components: the mode field conversion loss in the transition region from the conventional waveguide (small mode field) to the EC end face (large mode field); and the optical field overlap loss between the mode field of the EC end face and the mode field of the external optical fiber (i.e., the loss caused by non-ideal mode field matching).

[0005] In recent years, fiber arrays (FA) have been increasingly used in R&D, production testing, and mass production. During production testing or R&D, in order to verify performance indicators such as the coupling loss of the end-face coupler, some coupler test structures need to be built on the optical chip. The usual practice is to set up a loop structure at the edge of the chip, which includes two ECs and a curved waveguide connecting the two, as shown in Figure 1. The spacing between the two ECs is set to be equal to the channel spacing of the FA (for example, 250um), so that the chip can be docked with the FA, and the two channels of the FA are used to send light into and out of the chip respectively (as shown by the arrows in Figure 1), thereby testing the coupling loss of the EC. EC can support both TE and TM polarizations. Accordingly, the coupling loss of the EC under TE polarization and TM polarization needs to be tested (represented by solid and dotted lines, respectively).

[0006] However, the coupling loss measured by this method includes the on-chip mode field conversion loss and the light field overlap loss with the optical fiber, that is, the overall EC coupling loss. It is impossible to obtain the individual values ​​of the on-chip mode field conversion loss and the light field overlap loss with the optical fiber. Therefore, it is impossible to specifically analyze the source of each part of the loss to provide sufficiently comprehensive feedback for design improvement and iteration. If the two need to be separated, additional test structures need to be added, such as adding cascaded ECs and grating couplers (GCs) to test the mode field conversion loss on the chip, which takes up more chip space; and generally, the same GC cannot support both TE and TM polarizations at the same time. A set of test structures needs to be made for each polarization to test the mode field conversion loss under TE and TM polarizations respectively. In this way, since multiple test structures need to be set up to complete the above functions, this approach takes up chip space, reduces test efficiency, and increases costs.

[0007] Therefore, it is necessary to provide a new end coupler testing device, method and test array to solve the above problems existing in the prior art.

[0008] Summary of the Invention

[0009] The purpose of the present invention is to provide an end-face coupler testing device, method and test array, which can not only simultaneously test the coupling loss of TE polarized light and TM polarized light, but also decompose the on-chip mode field conversion loss and light field overlap loss, saving space within the chip, improving chip utilization efficiency and reducing costs.

[0010] To achieve the above-mentioned object, the end coupler testing device of the present invention is provided on an optical chip and includes:

[0011] A loop structure, provided on the optical chip, for coupling with an external optical fiber array;

[0012] A cascade test structure, provided on the optical chip, for testing the on-chip mode field conversion loss of TE polarized light and TM polarized light;

[0013] a polarization separation module, connected to the cascade test structure, for sending TE polarized light and TM polarized light into the cascade test structure for testing and then sending them out respectively;

[0014] A TE grating coupling module is connected to the input and output ends of the polarization separation module and is used to send TE polarized light into the cascade test structure and output it;

[0015] a TM grating coupling module, connected to the input and output ends of the polarization separation module, for sending TM polarized light into the cascade test structure and outputting it;

[0016] A calibration structure is used to obtain calibration data of the TE polarized light and the TM polarized light.

[0017] The beneficial effects of the end coupler test device described in the present invention are: by providing a polarization separation module, a TE grating coupling module, and a TM grating coupling module, TE polarized light and TM polarized light can be respectively transmitted to a cascade test structure for coupling testing, so that the TE polarized light and TM polarized light can be respectively exported after passing through the polarization separation module, so that the on-chip mode field conversion loss of the TE polarized light and TM polarized light can be respectively tested through the same cascade test structure, which is beneficial to saving on-chip space and improving test efficiency.

[0018] Optionally, the cascade test structure includes a first curved waveguide and an end face coupler group, the end face coupler group includes a first end face coupler, a second end face coupler, a third end face coupler, and a fourth end face coupler, one end of the first end face coupler is connected to one end of the third end face coupler, the other end of the first end face coupler is connected to one end of the second end face coupler through the first curved waveguide, the other end of the second end face coupler is connected to one end of the fourth end face coupler, and the other ends of the third end face coupler and the fourth end face coupler are both connected to the polarization separation module.

[0019] Optionally, the polarization separation module includes a first polarization separator and a second polarization separator, the input end of the first polarization separator includes a first TE input end and a first TM input end, the output end of the first polarization separator is electrically connected to the cascade test structure, the input end of the second polarization separator is electrically connected to the output end of the cascade test structure, the output end of the second polarization separator includes a first TE output end and a first TM output end, the TE grating coupling module includes a first TE grating coupler and a second TE grating coupler, and the TM grating coupling module includes a first TM grating coupler and a second TM grating coupler. After the TE polarized light passes through the first TE grating coupler and is input to the first TE input end, it is sent into the cascade test structure and sent to the second TE grating coupler through the first TE output end. After the TM polarized light passes through the first TM grating coupler and is input to the first TM input end, it is sent into the cascade test structure and sent to the second TM grating coupler through the first TM output end.

[0020] Optionally, the calibration structure includes a third polarization separator, a fourth polarization separator, a third TE grating coupler, a fourth TE grating coupler, a third TM grating coupler and a fourth TM grating coupler. The output end of the third polarization separator is connected to the input end of the fourth polarization separator through a second curved waveguide. The input end of the third polarization separator includes a second TE input end and a second TM input end. The output end of the fourth polarization separator includes a second TE output end and a second TM output end. After the TE polarized light passes through the third TE grating coupler and is sent into the second TE input end, it passes through the third polarization separator and the fourth polarization separator in sequence and is sent to the fourth TE grating coupler through the second TE output end. After the TM polarized light passes through the third TM grating coupler and is sent into the second TM input end, it passes through the third polarization separator and the fourth polarization separator in sequence and is sent to the fourth TM grating coupler through the second TM output end. The beneficial effect is that by setting up a calibration structure, the losses of GC, PS, and curved waveguide are de-embedded in both TE polarized light and TM polarized light, so as to extract the coupling loss of each end face coupler, and the optical field overlap loss of each end face coupler is obtained based on the above-calculated on-chip mode field conversion loss, thereby accurately obtaining the respective values ​​of the optical field overlap loss and the on-chip mode field conversion loss. This improves test efficiency while saving space within the chip and reducing costs.

[0021] Optionally, the loop structure includes a fifth end face coupler and a sixth end face coupler, the fifth end face coupler and the sixth end face coupler are connected by a third curved waveguide, a cutting path is provided on the optical chip, and the ends of the fifth end face coupler and the sixth end face coupler close to the TE grating coupling module are both located on the cutting path, the connection between the first end face coupler and the third end face coupler, and the connection between the second end face coupler and the fourth end face coupler are both located on the cutting path, and the loop structure is nested with the loop formed between the first end face coupler, the first curved waveguide, and the second end face coupler. The beneficial effect is that the nested relationship between the loop structure and the loop formed between the first end face coupler, the first curved waveguide, and the second end face coupler can save space and reduce costs.

[0022] Optionally, the first end face coupler, the second end face coupler, the fifth end face coupler and the sixth end face coupler all form an angle A with the straight line where the cutting lane is located, wherein 0°<A<180°.

[0023] Optionally, a first connection area is provided between the first end face coupler and the third end face coupler, a second connection area is provided between the second end face coupler and the fourth end face coupler, and the cutting path is provided on the first connection area and the second connection area.

[0024] Optionally, a third connection region is provided at one end of the fifth end face coupler close to the cutting street, and a fourth connection region is provided at one end of the sixth end face coupler close to the cutting street.

[0025] Optionally, a gap is provided between the third connection area and the fourth connection area and the cutting street.

[0026] Optionally, the first connection area, the second connection area, the third connection area and the fourth connection area are all arranged on the cutting street.

[0027] Optionally, a first etching area and a second etching area are provided on the cutting street.

[0028] Optionally, the first etched region at least partially overlaps with the third connection region, and the second etched region at least partially overlaps with the fourth connection region.

[0029] Optionally, a gap is provided between the first etched region and the fifth end face coupler, and a gap is provided between the second etched region and the sixth end face coupler.

[0030] Optionally, the loopback structure is arranged inside the cascade test structure.

[0031] Optionally, the end of the fifth end face coupler and the end of the sixth end face coupler are arranged on different end faces of the chip.

[0032] Optionally, the number of the end face coupler groups is at least two, and the ends of adjacent end face coupler groups are connected to each other.

[0033] Optionally, the first polarization separator, the second polarization separator, the third polarization separator and the fourth polarization separator are all replaced by polarization separation rotators, and the first TM grating coupler, the second TM grating coupler, the third TM grating coupler and the fourth TM grating coupler are all replaced by TE grating couplers.

[0034] The present invention also provides an end coupler testing method, which is applied to the above-mentioned end coupler testing device. The end coupler testing method includes:

[0035] Before chip cutting, the initial polarized light is input into a TE grating coupling module or a TM grating coupling module according to the type of the initial polarized light, and is tested by the cascade test structure to obtain a first polarized light, wherein the power of the initial polarized light is P0 and the power of the first polarized light is P1;

[0036] Inputting the initial polarized light into the calibration structure to obtain calibrated polarized light, wherein the power of the calibrated polarized light is P2;

[0037] The on-chip mode field conversion loss of each end coupler in the cascade test structure is calculated according to the power P1 of the first polarized light and the power P2 of the calibration polarized light.

[0038] The beneficial effect of the end face coupler testing method of the present invention is that: TE or TM polarized light is sent into the cascade test structure through the TE or TM grating coupling module for testing to obtain the corresponding output first polarized light, and then calibrated by the calibration structure to obtain calibrated polarized light, and then the on-chip mode field conversion loss of each end face coupler is calculated according to the power of the first polarized light and the calibrated polarized light.

[0039] Optionally, the method further includes:

[0040] After the chip is cut along the cutting street, the initial polarized light is input into the loop structure through the fifth end face coupler and the third polarized light is output from the sixth end face coupler, where the power of the third polarized light is P3;

[0041] Calculating the coupling loss of each end coupler in the loop structure according to the power of the initial polarized light and the power of the third polarized light;

[0042] The optical field overlapping loss is calculated based on the on-chip mode field conversion loss and coupling loss.

[0043] The present invention also discloses a test array, comprising a plurality of the above-mentioned end face coupler test devices, wherein the plurality of end face coupler test devices are arrayed on an optical chip, and each of the end face coupler test devices is not completely the same. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] FIG1 is a schematic diagram of a test structure of an end face coupler docking with an optical fiber array in the prior art;

[0045] FIG2 is a schematic structural diagram of the end coupler testing device of the present invention;

[0046] FIG3 is a schematic diagram of the end coupler test device of the present invention being connected to an optical fiber array after cutting;

[0047] 4 is a schematic structural diagram of the end coupler test device of the present invention when the cascade test structure includes 4N end couplers;

[0048] 5 is a schematic structural diagram of the end face coupler testing device of the present invention when the end face coupler is tilted;

[0049] FIG6 is a schematic structural diagram of the end coupler testing device according to the present invention when a first connection area and a second connection area are provided;

[0050] 7 is a schematic structural diagram of the end coupler testing device according to the present invention when a third connection area and a fourth connection area are provided;

[0051] 8 is a schematic structural diagram of the end face coupler testing device according to the present invention, in which the first connection area, the second connection area, the third connection area, and the fourth connection area are all arranged on the cutting path;

[0052] FIG9 is a schematic structural diagram of a first etching area and a second etching area in the end coupler testing device according to the present invention;

[0053] FIG10 is a schematic structural diagram of the end coupler testing device according to the present invention when the etching area and the connection area partially overlap;

[0054] FIG11 is a schematic structural diagram of the end coupler test device according to the present invention when a polarization separation rotator is used;

[0055] FIG12 is a schematic structural diagram of the end coupler test device according to the present invention when the loopback structure is arranged inside the cascade test structure;

[0056] 13 is a schematic structural diagram of the end coupler testing device of the present invention when the fifth end coupler and the sixth end coupler are arranged relative to each other;

[0057] FIG14 is a flow chart of the end coupler testing method of the present invention;

[0058] FIG15 is a schematic diagram of the structure of the test array of the present invention. DETAILED DESCRIPTION

[0059] In order to make the purpose, technical solutions and advantages of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention. Unless otherwise defined, the technical terms or scientific terms used herein should be the common meanings understood by people with ordinary skills in the field to which the present invention belongs. The words "including" and similar words used in this article mean that the elements or objects appearing before the word cover the elements or objects listed after the word and their equivalents, without excluding other elements or objects.

[0060] To address the problems existing in the prior art, an embodiment of the present invention provides an end coupler testing device, which is disposed on an optical chip 10 and includes, as shown in FIG2 :

[0061] A loop structure 20 is provided on the optical chip 10 and is used for coupling with an external optical fiber array;

[0062] A cascade test structure 30 is provided on the optical chip 10 and is used to test the on-chip mode field conversion loss of TE polarized light and TM polarized light;

[0063] a polarization separation module 40 connected to the cascade test structure 30 and configured to send TE polarized light and TM polarized light into the cascade test structure 30 and then send them out;

[0064] A TE grating coupling module 50 is connected to the input and output ends of the polarization separation module 40 and is used to send TE polarized light into the cascade test structure 30 and output it;

[0065] a TM grating coupling module 60 connected to the input and output ends of the polarization separation module 40 and configured to feed TM polarized light into the cascade test structure 30 and output the TM polarized light;

[0066] The calibration structure 70 is used to obtain calibration data of the TE polarized light and the TM polarized light.

[0067] In this embodiment, on the basis of the conventional loop structure 20, a cascade test structure 30 is added to test TE polarized light and TM polarized light. Since the TE grating coupling module 50 and the TM grating coupling module 60 share a cascade test structure 30 for testing, the internal space occupied by the chip can be effectively reduced. Under the action of the polarization separation module 40, TE polarized light and TM polarized light are respectively sent into and out of the cascade test structure 30 through the polarization separation module 40 for testing, so as to test the on-chip mode field conversion loss in the TE and TM polarization states, thereby improving the testing efficiency of the chip.

[0068] It should be noted that in the subsequent solutions, the structural description of the polarization separation module 40 and the calibration module 50 is primarily specific to the directions indicated by the arrows in FIG2 . The so-called input here can also be used as output, and the so-called output can also be used as input. In other words, the directions of input and output light are interchangeable and are not limited to the directions indicated by the arrows in FIG2 , and will not be further described here.

[0069] In some embodiments, with continued reference to FIG2 , the cascade test structure 30 includes a first curved waveguide 307 and an end coupler group, wherein the end coupler group includes a first end coupler 301, a second end coupler 302, a third end coupler 303, and a fourth end coupler 304. One end of the first end coupler 301 is connected to one end of the third end coupler 303, the other end of the first end coupler 301 is connected to one end of the second end coupler 302 via the first curved waveguide 307, the other end of the second end coupler 302 is connected to one end of the fourth end coupler 304, and the other ends of the third end coupler 303 and the fourth end coupler 304 are both connected to the polarization separation module 40. The polarization separation module 40 includes a first polarization separator 401 and a second polarization separator 402. The input end of the first polarization separator 401 includes a first TE input end and a first TM input end. The output end of the first polarization separator 401 is electrically connected to the cascade test structure 30. The input end of the second polarization separator 402 is electrically connected to the output end of the cascade test structure 30. The output end of the second polarization separator 402 includes a first TE output end and a first TM output end. The TE grating coupling module 50 includes a first TE grating coupler 501 and a second TE grating coupler 502. The TM grating coupling module 60 It includes a first TM grating coupler 601 and a second TM grating coupler 602. After the TE polarized light passes through the first TE grating coupler 501 and is input to the first TE input end, it is sent into the cascade test structure 30 and sent out to the second TE grating coupler 502 through the first TE output end. After the TM polarized light passes through the first TM grating coupler 601 and is input to the first TM input end, it is sent into the cascade test structure 30 and sent out to the second TM grating coupler 602 through the first TM output end.

[0070] It should be noted that the polarization separation module 40 can be used to separate two polarized lights or to combine two polarized lights. This structure is a reversible structure and is selected according to actual usage scenarios and needs.

[0071] In this embodiment, the calibration structure 70 is used to obtain calibration data of the TE polarized light and the TM polarized light. The calibration structure 70 includes a third polarization separator 701, a fourth polarization separator 702, a third TE grating coupler 703, a fourth TE grating coupler 704, a third TM grating coupler 705 and a fourth TM grating coupler 706. The output end of the third polarization separator 701 is connected to the input end of the fourth polarization separator 702 through a second curved waveguide 707. The input end of the third polarization separator 701 includes a second TE input end and a second TM input end. The fourth polarization separator 702 includes a third TE grating coupler 703, a fourth TE grating coupler 704, a third TM grating coupler 705 and a fourth TM grating coupler 706. The output end of 02 includes a second TE output end and a second TM output end. After the TE polarized light passes through the third TE grating coupler 703 and is sent into the second TE input end, it passes through the third polarization separator 701 and the fourth polarization separator 702 in sequence and is sent out through the second TE output end to the fourth TE grating coupler 704. After the TM polarized light passes through the third TM grating coupler 705 and is sent into the second TM input end, it passes through the third polarization separator 701 and the fourth polarization separator 702 in sequence and is sent out through the second TM output end to the fourth TM grating coupler 706.

[0072] For example, the first end face coupler 301 is recorded as EC#2, the second end face coupler 302 is recorded as EC#3, the third end face coupler 303 is recorded as EC#5, the fourth end face coupler 304 is recorded as EC#6, the first polarization separator 401 is recorded as PS#1, the second polarization separator 402 is recorded as PS#2, the first TE grating coupler 501 is recorded as TE GC#1, the second TE grating coupler 502 is recorded as TE GC#2, the first TM grating coupler 601 is recorded as TM GC#1, the second TM grating coupler 602 is recorded as TM GC#2, the third polarization separator 701 is recorded as PS#3, the fourth polarization separator 702 is recorded as PS#4, the third TE grating coupler 703 is recorded as TE GC#3, the fourth TE grating coupler 704 is recorded as TE GC#4, and the third TM grating coupler 705 is recorded as TM GC#3, the fourth TM grating coupler 706 is recorded as TM GC#4. Referring to FIG2 , the test of TE polarized light is taken as an example. First, TE polarized light with an initial power of P0 is input through the first TE grating coupler 501 and then transmitted to the first polarization separator 401. Then, it passes through the third end face coupler 303, the first end face coupler 301, the second end face coupler 302, the fourth end face coupler 304, and the second polarization separator 402. The power of the light sent out through the second TE grating coupler 502 is P1_TE. Then, the TE polarized light with an initial power of P0 is also sent into the calibration structure 70. After passing through the third TE grating coupler 703, the third polarization separator 701, the fourth polarization separator 702 and the fourth TE grating coupler 704, the optical signal is sent out. The power of the sent optical signal is P2_TE. Then, the on-chip mode field conversion loss IL_1_TE of each end face coupler in the cascade test structure 30 for TE polarized light is (P1_TE-P2_TE) / 4. Similarly, TM polarized light with power P0 enters the first polarization separator 401 from the first TM grating coupler 601, and passes through the third end face coupler 303, the first end face coupler 301, the second end face coupler 302, and the fourth end face coupler 304 in sequence, then passes through the second polarization separator 402 and the second TM grating coupler 602 to send out the optical signal. The power of the sent optical signal is P1_TM. The TM polarized light with power P0 is sent into the calibration structure 70, and passes through the third TM grating coupler 705, the third polarization separator 701, the fourth polarization separator 702, and the fourth TM grating coupler 706 in sequence to send out the optical signal. The power of the sent optical signal is P2_TM. The on-chip mode field conversion loss IL_1_TM of each end face coupler EC in the cascade test structure 30 for TM polarized light is (P1_TM-P2_TM) / 4. Through the above calculation method, the on-chip mode field conversion loss of each end coupler EC can be calculated.

[0073] In this embodiment, the loop structure 20 includes a fifth end face coupler 201 and a sixth end face coupler 202, and the fifth end face coupler 201 and the sixth end face coupler 202 are connected by a third curved waveguide 205. A cutting path 80 is provided on the optical chip 10, and the ends of the fifth end face coupler 201 and the sixth end face coupler 202 close to the TE grating coupling module 50 are both located on the cutting path 80. The connection between the first end face coupler 301 and the third end face coupler 303, and the connection between the second end face coupler 302 and the fourth end face coupler 304 are both located on the cutting path 80. The loop structure 20 and the loop formed between the first end face coupler 301, the first curved waveguide 307, and the second end face coupler 302 are in a nested relationship to save chip space and reduce costs. Since the loop structure 20 is provided on the optical chip 10 , in order to further test the coupling loss of each end coupler EC, the loop structure 20 can be used to further test the coupling loss of each end coupler EC.

[0074] Exemplarily, referring to FIG3 , the optical chip 10 is cut along the cutting path 80 so that the first end face coupler 301, the third end face coupler 303, the fifth end face coupler 202, and the sixth end face coupler 202 on the left side of the optical chip 10 form an independent chip. The TE polarized light and TM polarized light with a power of P0 previously tested are coupled to the optical fiber array 90 using conventional methods for testing. Specifically, taking the TE polarized light with a power of P0 as an example, the output power of the TE polarized light after passing through the loop structure 10 formed by the fifth end face coupler 202 and the sixth end face coupler 202 of the TE polarized light is P3_TE. The coupling loss of the end face coupler for the TE polarized light is IL_TE = (P3_TE-P0) / 2. Based on the intra-chip mode field conversion loss IL_1_TE for the TE polarized light calculated above, the optical field overlap loss IL_2_TE between the end face coupler and the optical fiber can be calculated as IL_TE = IL_TE-IL_1_TE. Similarly, the output power of TM polarized light with power P0 after passing through the loop structure 10 is P3_TM, then the coupling loss of the end face coupler to the TM polarized light is IL_TM = (P3_TM-P0) / 2. Based on the above-calculated on-chip mode field conversion loss IL_1_TM for TM polarized light, the optical field overlapping loss between the end face coupler and the optical fiber can be calculated as IL_2_TM = IL_TM-IL_1_TM.

[0075] Therefore, the test device of this solution can test the coupling loss of TE polarized light and TM polarized light separately, and can decompose the intra-chip mode field conversion loss and the light field overlap loss with the optical fiber, which not only saves space within the chip, but also improves utilization efficiency and reduces costs.

[0076] It should be noted that in the cascade test structure 30, the number of the end face coupler groups is at least two, and the ends of adjacent end face coupler groups are connected to each other. Referring to Figure 4, the number of end face couplers is not limited to four, and can be 4N, where N is a positive integer, to facilitate cascade testing.

[0077] In some embodiments, referring to FIG5 , the first end-face coupler 301, the second end-face coupler 302, the fifth end-face coupler 201, and the sixth end-face coupler 202 all form an angle A with the line along the dicing street 80, where 0°<A<180°. By setting a certain angle A, light reflection at the coupling end faces can be reduced.

[0078] Exemplarily, the angle A=90°, that is, the first end face coupler 301 , the second end face coupler 302 , the fifth end face coupler 201 and the sixth end face coupler 202 are all perpendicular to the straight line where the cutting street 80 is located.

[0079] In some other embodiments, referring to Figure 6, a first connection area 305 is provided between the first end face coupler 301 and the third end face coupler 303, and a second connection area 306 is provided between the second end face coupler 302 and the fourth end face coupler 304. The cutting path 80 is provided on the first connection area 305 and the second connection area 306. The waveguide widths of the first connection area 305 and the second connection area 306 are uniform, and the width of the first connection area 305 is equal to the width of the end of the first end face coupler 301 and the width of the end of the third end face coupler 303. The width of the second connection area 306 is equal to the width of the end of the second end face coupler 302 and the width of the end of the fourth end face coupler 304.

[0080] Furthermore, a gap is set between the ends of the fifth end face coupler 201 and the sixth end face coupler 202 and the cutting path 80 to protect the end face couplers, that is, to ensure that when cutting along the cutting path 80, there will be no impact on the ends of the fifth end face coupler 201 and the sixth end face coupler 202, such as rough end faces, cracks, wrinkles, burrs, etc., so that the coupling loss can be tested normally after cutting.

[0081] In yet other embodiments, referring to FIG7 , a third connection region 203 is provided at one end of the fifth end face coupler 201 proximate to the dicing street 80, and a fourth connection region 204 is provided at one end of the sixth end face coupler 202 proximate to the dicing street 80. A gap is provided between the third connection region 203 and the fourth connection region 204 and the dicing street 80. The third connection region 203 and the fourth connection region 204 protect the end face couplers, ensuring that cutting along the dicing street 80 does not cause any impact, such as roughness, cracks, wrinkles, or burrs, on the fifth and sixth end face couplers 201 and 202.

[0082] In some embodiments, referring to Figure 8, the first connection area 305, the second connection area 306, the third connection area 203 and the fourth connection area 204 are all arranged on the cutting road 80, so that when cutting the chip along the cutting road 80, the cutting offset will not be caused due to insufficient control of the cutting position accuracy, thereby causing the cut end waveguide width to be uncontrollable.

[0083] In yet other embodiments, referring to FIG9 , a first etching region 801 and a second etching region 802 are provided on the cutting path 80. By providing the first etching region 801 and the second etching region 802, the impact of the end face roughness caused by cutting on the end face coupler can be reduced. Semiconductor etching processes are used to etch a portion of the end face, resulting in good flatness of the etched end face, thereby improving the coupling effect. Etching is not performed between the first end face coupler 301 and the second end face coupler 302, and between the third end face coupler 303 and the fourth end face coupler 304, to ensure the continuity of the cascade test structure 30, so that the on-chip mode field conversion test can be performed normally before cutting.

[0084] In some embodiments, a gap is provided between the first etched region 801 and the fifth end face coupler 201 , and a gap is provided between the second etched region 802 and the sixth end face coupler 202 , so as to avoid damage to the end of the loop structure 10 caused by etching.

[0085] In yet other embodiments, referring to FIG10 , the first etched region 801 at least partially overlaps the third connection region 203, and the second etched region 802 at least partially overlaps the fourth connection region 204. By at least partially overlapping the first etched region 801 and the third connection region 203, and at least partially overlapping the second etched region 802 and the fourth connection region 204, when the chip is cut along the dicing street 80, insufficient control over the cutting position accuracy will prevent cutting deviation, which in turn will prevent the width of the cut facet waveguide from being uncontrollable.

[0086] 21. In some other embodiments, referring to FIG11 , the polarization splitter in the polarization separation module 40 may also employ a polarization splitter rotator (PSR). At the same time, the grating coupler for TM polarization is also converted to a grating coupler for TE polarization. That is, the first polarization splitter 401, the second polarization splitter 402, the third polarization splitter 701, and the fourth polarization splitter 702 are all replaced with polarization splitter rotators, and the first TM grating coupler 601, the second TM grating coupler 602, the third TM grating coupler 705, and the fourth TM grating coupler 706 are all replaced with TE grating couplers. TE polarized light can be converted to TM polarization, similarly enabling testing of two polarization states. For example, TE polarized light can enter TE GC#1, pass through PSR#1, maintain TE polarization, enter the cascaded EC, and then pass through PSR#2 before exiting TE GC#3. If TE polarized light enters from TE GC#2, it will be converted to TM polarized light after passing through PSR#1; this TM polarized light passes through the cascade EC, and then through PSR#2 to be converted back to TE polarized light, and then exits from TE GC#4.

[0087] For example, the incident light power is P0 and the polarization state is set to TE. The light enters from TE GC#1, passes through the cascade test structure of 2 PSRs and 4 end-face couplers, and then exits from TE GC#3 with a power of P1_TE. With the same light source power, the light enters the calibration structure from TE GC#5, and then passes through 2 PSRs and exits from TE GC#7 with a power of P2_TE. The on-chip mode field conversion loss of each EC is IL_1_TE = (P1_TE-P2_TE) / 4. Similarly, TE polarized light enters TE GC #2, passes through the cascaded structure of two PSRs and four ECs, and exits TE GC #4 with a power of P1_TM. Similarly, light from TE GC #6 enters the calibration structure, passes through two PSRs, and exits TE GC #8 with a power of P2_TM. The on-chip mode conversion loss of each EC, IL_1_TM, is calculated as (P1_TM - P2_TM) / 4. Since the test process is essentially the same as described above, it is not repeated here. P1_TE, P2_TE, P1_TM, and P2_TM are in dBm, and IL_1_TE and IL_1_TM are in dB.

[0088] In some embodiments, referring to Figure 12, the loop structure 20 is disposed inside the cascade test structure 30. In some embodiments, the loop structure 20 may not be nested inside and outside the cascade test structure 30, but may be located in different positions (not shown).

[0089] Furthermore, referring to FIG13 , an end portion of the fifth end face coupler 201 and an end portion of the sixth end face coupler 202 are arranged opposite to each other.

[0090] It should be noted that the present invention does not impose any particular limitation on the arrangement positions, directions, and angles formed with the end faces of the fifth end face coupler 201 and the sixth end face coupler 202 , and will not be further elaborated here.

[0091] The test device of the present invention is provided with a TE grating coupling module, a TM grating coupling module and a polarization separation module so that TE polarized light and TM polarized light can be transmitted to a cascade test structure for coupling testing, respectively. In addition, the on-chip mode field conversion loss of TE polarized light and TM polarized light can be tested separately through the cascade test structure, which is beneficial to saving on-chip space and improving test efficiency. Moreover, the respective values ​​of mode field conversion loss and light field overlap loss can be measured separately through a nested loop structure and a reasonable setting of cutting paths.

[0092] The present invention also discloses a method for testing an end coupler, which is applied to the above-mentioned end coupler testing device. Referring to FIG. 14 , the method for testing an end coupler includes the following steps:

[0093] S1401. Before chip cutting, input the initial polarized light into a TE grating coupling module or a TM grating coupling module according to the type of the initial polarized light, and obtain first polarized light after being tested by the polarization separation module and the cascade test structure, wherein the power of the initial polarized light is P0 and the power of the second polarized light is P1;

[0094] S1402, inputting the initial polarized light into the calibration structure to obtain calibrated polarized light, wherein the power of the calibrated polarized light is P2;

[0095] S1403 : Calculate the on-chip mode field conversion loss of each end coupler in the cascade test structure according to the power P1 of the first polarized light and the power P2 of the calibration polarized light.

[0096] Among them, the on-chip mode-field conversion loss IL_1 = (P1-P2) / 4.

[0097] Furthermore, the method further comprises:

[0098] S1404 , after the chip is cut, input the initial polarized light into the loop structure to output a third polarized light, where the power of the third polarized light is P3.

[0099] S1405 : Calculate the coupling loss of each end coupler in the loop structure according to the power of the initial polarized light and the power of the third polarized light.

[0100] Where, coupling loss IL = (P3-P0) / 2

[0101] S1406 : Calculate the optical field overlap loss according to the on-chip mode field conversion loss and coupling loss.

[0102] Among them, the light field overlap loss IL_2 = IL-IL_1

[0103] Since the process and principle of the above method correspond one-to-one to the working process of the aforementioned end face coupler testing device, they will not be described in detail here.

[0104] The present invention also discloses a test array, referring to FIG15 , comprising a plurality of the above-mentioned end face coupler test devices, wherein the plurality of end face coupler test devices are arrayed on an optical chip, and each of the end face coupler test devices is not exactly the same.

[0105] Some design parameters of each test device in the test array can be set to be the same or different to facilitate experimental design, and all test structures share the same dicing lane.

[0106] The integrated material platform on which the above-mentioned test structure is located includes bulk silicon, silicon on insulator, silicon on sapphire, silicon dioxide, aluminum oxide, indium phosphide, lithium niobate, and polymer. The waveguide types of the test structure include channel waveguides, ridge waveguides, slot waveguides, diffused waveguides, and photonic crystal waveguides. The operating wavelength range of the test structure includes the visible light band, O band, E band, S band, C band, L band, U band, and mid-infrared band; the operating wavelengths of the various test structures in the array shown can be the same wavelength or different wavelengths. The application fields of the test structure include lidar, beam control, optical sensing, optical interconnection, free space optical communication, optical storage, optical computing, etc. The structural design of the EC can include but is not limited to an inverted cone, a stepped inverted cone, a cantilever beam, a side groove, a V-shaped ground groove, multiple waveguides, a multi-layer waveguide, a subwavelength structure, etc. The structural design of the PS and PSR includes but is not limited to an adiabatic coupler, a bent coupler, a directional coupler, a Y-shaped branch, a multi-mode interference structure, a subwavelength structure, etc. The structural design of the GC includes but is not limited to straight grating, fan-shaped curved grating, dual polarization grating, multi-layer material grating, etc. The shape of the curved waveguide includes but is not limited to arc shape, linear curved shape, Euler curved shape or sinusoidal shape.

[0107] While the embodiments of the present invention have been described in detail above, it will be apparent to those skilled in the art that various modifications and variations of these embodiments are possible. However, it should be understood that such modifications and variations are within the scope and spirit of the present invention as set forth in the claims. Furthermore, the invention described herein is susceptible to other embodiments and may be practiced or implemented in a variety of ways.

Claims

1. An end coupler testing device, arranged on an optical chip, comprising: A loop structure, arranged on the optical chip, for coupling with an external optical fiber array; A cascade test structure, arranged on the optical chip, for testing the on-chip mode field conversion loss of TE polarized light and TM polarized light; A polarization separation module, connected to the cascade test structure, for sending TE polarized light and TM polarized light into the cascade test structure for testing and then sending them out respectively; A TE grating coupling module, connected to the input end and the output end of the polarization separation module, and used for sending TE polarized light into the cascade test structure and exporting it; A TM grating coupling module, connected to the input end and the output end of the polarization separation module, and used for sending TM polarized light into the cascade test structure and exporting it; The calibration structure is used to obtain calibration data of the TE polarized light and the TM polarized light.

2. The end coupler testing device according to claim 1, characterized in that: The cascade test structure includes a first curved waveguide and an end face coupler group, the end face coupler group includes a first end face coupler, a second end face coupler, a third end face coupler, and a fourth end face coupler, one end of the first end face coupler is connected to one end of the third end face coupler, the other end of the first end face coupler is connected to one end of the second end face coupler through the first curved waveguide, the other end of the second end face coupler is connected to one end of the fourth end face coupler, and the other ends of the third end face coupler and the fourth end face coupler are both connected to the polarization separation module.

3. The end coupler testing device according to claim 2, characterized in that: The polarization separation module includes a first polarization separator and a second polarization separator, the input end of the first polarization separator includes a first TE input end and a first TM input end, the output end of the first polarization separator is electrically connected to the cascade test structure, the input end of the second polarization separator is electrically connected to the output end of the cascade test structure, the output end of the second polarization separator includes a first TE output end and a first TM output end, the TE grating coupling module includes a first TE grating coupler and a second TE grating coupler, the TM grating coupling module includes a first TM grating coupler and a second TM grating coupler, the TE polarized light is input to the first TE input end through the first TE grating coupler, and then sent to the cascade test structure and sent to the second TE grating coupler through the first TE output end, the TM polarized light is input to the first TM input end through the first TM grating coupler, and then sent to the cascade test structure and sent to the second TM grating coupler through the first TM output end.

4. The end coupler testing device according to any one of claim 2, characterized in that: The number of the end face coupler groups is at least two, and the ends of adjacent end face coupler groups are connected to each other.

5. The end coupler testing device according to claim 4, characterized in that: The calibration structure includes a third polarization separator, a fourth polarization separator, a third TE grating coupler, a fourth TE grating coupler, a third TM grating coupler and a fourth TM grating coupler. The output end of the third polarization separator is connected to the input end of the fourth polarization separator through a second curved waveguide. The input end of the third polarization separator includes a second TE input end and a second TM input end. The output end of the fourth polarization separator includes a second TE output end and a second TM output end. After the TE polarized light is sent into the second TE input end through the third TE grating coupler, it passes through the third polarization separator and the fourth polarization separator in sequence and is sent to the fourth TE grating coupler through the second TE output end. After the TM polarized light is sent into the second TM input end through the third TM grating coupler, it passes through the third polarization separator and the fourth polarization separator in sequence and is sent to the fourth TM grating coupler through the second TM output end.

6. The end coupler testing device according to claim 3, characterized in that: The loop structure includes a fifth end face coupler and a sixth end face coupler, the fifth end face coupler and the sixth end face coupler are connected via a third curved waveguide, a cutting path is provided on the optical chip, one end of the fifth end face coupler and the sixth end face coupler close to the TE grating coupling module are both located on the cutting path, a connection between the first end face coupler and the third end face coupler, and a connection between the second end face coupler and the fourth end face coupler are both located on the cutting path, and the loop structure is in a nested relationship with the loop formed between the first end face coupler, the first curved waveguide, and the second end face coupler.

7. The end coupler testing device according to claim 6, characterized in that: The first end face coupler, the second end face coupler, the fifth end face coupler and the sixth end face coupler all form an angle A with the straight line where the cutting path is located, wherein 0°<A<180°.

8. The end coupler testing device according to claim 6, characterized in that: A first connection area is provided between the first end face coupler and the third end face coupler, a second connection area is provided between the second end face coupler and the fourth end face coupler, and the cutting road is provided on the first connection area and the second connection area.

9. The end coupler testing device according to claim 8, characterized in that: A third connection area is disposed at one end of the fifth end face coupler close to the cutting path, and a fourth connection area is disposed at one end of the sixth end face coupler close to the cutting path.

10. The end coupler testing device according to claim 9, characterized in that: A gap is provided between the third connection area and the fourth connection area and the cutting street.

11. The end coupler testing device according to claim 9, characterized in that: The first connection area, the second connection area, the third connection area and the fourth connection area are all arranged on the cutting street.

12. The end coupler testing device according to claim 9, characterized in that: A first etching area and a second etching area are arranged on the cutting road.

13. The end coupler testing device according to claim 12, characterized in that: The first etched region at least partially overlaps with the third connection region, and the second etched region at least partially overlaps with the fourth connection region.

14. The end coupler testing device according to claim 12, characterized in that: A gap is provided between the first etched region and the fifth end face coupler, and a gap is provided between the second etched region and the sixth end face coupler.

15. The end coupler testing device according to claim 6, characterized in that: The loop structure is arranged inside the cascade test structure.

16. The end coupler testing device according to claim 6, characterized in that: An end portion of the fifth end face coupler and an end portion of the sixth end face coupler are arranged on different end faces of the chip.

17. The end coupler testing device according to claim 5, characterized in that: The first polarization separator, the second polarization separator, the third polarization separator and the fourth polarization separator are all replaced by polarization separation rotators, and the first TM grating coupler, the second TM grating coupler, the third TM grating coupler and the fourth TM grating coupler are all replaced by TE grating couplers.

18. A method for testing an end coupler, characterized in that: Applicable to the end coupler testing device of claim 4, the end coupler testing method comprising: Before chip cutting, according to the type of the initial polarized light, the initial polarized light is input into the TE grating coupling module or the TM grating coupling module, and is tested by the cascade test structure to obtain the first polarized light, wherein the power of the initial polarized light is P0, and the power of the first polarized light is P1; Inputting the initial polarized light into the calibration structure to obtain calibrated polarized light, wherein the power of the calibrated polarized light is P2; The on-chip mode field conversion loss of each end coupler in the cascade test structure is calculated according to the power P1 of the first polarized light and the power P2 of the calibration polarized light.

19. The end coupler testing method according to claim 18, characterized in that: The method further comprises: After the chip is cut along the cutting path, the initial polarized light is input into the loop structure through the fifth end face coupler and the third polarized light is output from the sixth end face coupler, and the power of the third polarized light is P3; Calculating the coupling loss of each end coupler in the loop structure according to the power of the initial polarized light and the power of the third polarized light; The optical field overlapping loss is calculated according to the on-chip mode field conversion loss and coupling loss.

20. A test array, characterized in that: It comprises a plurality of end face coupler test devices according to any one of claims 1 to 17, wherein the plurality of end face coupler test devices are arranged in an array on an optical chip, and each of the end face coupler test devices is not completely the same.

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