On-chip end face coupler test structure

Abstract

The invention relates to an on-chip end face coupler test structure, which comprises an optical coupling incident assembly and an optical coupling emergent assembly, and is characterized in that the optical coupling incident assembly is used for transmitting light from one end of a to-be-tested assembly to the to-be-tested assembly, the to-be-tested assembly comprises a plurality of coupler pairs cascaded along the light transmission direction, and the coupler pairs are used for transmitting the light to the to-be-tested assembly. The coupler pair comprises two end face couplers which are arranged in a butt joint mode, and the head ends and the tail ends of the two end face couplers are opposite in the light transmission direction. The optical coupling emitting assembly is used for emitting light emitted from the other end of the to-be-detected assembly. According to the invention, the loss caused by coupling interface mode field mismatch can be eliminated, so that the loss caused by the mode conversion efficiency can be accurately measured, the mode conversion loss test and process problem positioning and evaluation of the end face coupler can be realized, and the end face coupler is optimized to obtain the end face coupler with higher coupling efficiency.

Description

Technical Field

[0001] The present application relates to the field of semiconductor technology, and in particular to an on-chip end-face coupler test structure. Background Art

[0002] In recent years, silicon photonic integrated circuits have risen rapidly. As the core material of the microelectronics industry, silicon not only has excellent electrical properties, but also has low-loss optical transmission performance in the near-infrared band, making it an ideal choice for building efficient optical communication components. In the manufacturing process, although the basis of silicon photonic integrated circuits is the standard CMOS process, including lithography, thin film deposition and etching, in order to adapt to the needs of specific photonic devices, in some cases it may be necessary to adjust process parameters or introduce additional processing steps. Among them, optical couplers, as the interface between silicon photonic integrated circuits and chips such as optical fibers and lasers, are important optical components in silicon photonic integrated circuits. The horizontal coupling method based on end-face couplers and the vertical coupling method based on grating couplers are the two main fiber coupling methods in silicon photonic integrated circuits.

[0003] Vertical coupling allows for a wider tolerance range, reducing the need for precision alignment. Coupling can be implemented at any location on the chip, providing greater design freedom. However, compared to horizontal coupling, vertical coupling involves more complex optical structure design and manufacturing processes, which may increase costs, and there may be long-term stability and reliability issues after packaging, requiring more testing and verification. Horizontal coupling technology is relatively mature and easy to implement multi-channel coupling, which is suitable for most silicon photonic chip mass production solutions.

[0004] However, in the design process of end coupler, the coupling efficiency of the end coupler depends on two key factors: first, the coupling efficiency of the optical coupling interface, that is, the degree of matching between the end face and the optical fiber or laser mode; second, the mode conversion efficiency, that is, whether the light can be efficiently converted into the propagation mode supported by the waveguide after entering the waveguide from the end face of the coupler without excessive reflection or scattering loss.

[0005] In the process of testing the coupling performance of the end coupler, the overall performance of the coupling efficiency can be tested and evaluated through a horizontal coupling table, and the mode field size and divergence angle after the coupled optical fiber and the end coupler are tested separately, and the mode matching loss is obtained by comparing the mode overlap. However, the loss caused by the mode conversion efficiency cannot be accurately measured. At the same time, at the manufacturing process level, high-quality manufacturing processes are crucial to maintaining the consistency and accuracy of design parameters, and any process defects may reduce the mode conversion efficiency. Summary of the invention

[0006] The embodiment of the present application provides an on-chip end face coupler test structure to solve the problem in the related art that it is difficult to accurately measure the loss caused by mode conversion efficiency.

[0007] The embodiment of the present application provides an on-chip end face coupler test structure, which includes:

[0008] An optical coupling incident component, which is used to transmit light from one end of the component to be tested to the component to be tested, wherein the component to be tested includes a plurality of coupler pairs cascaded along the light transmission direction, the coupler pair includes two end face couplers butted against each other, and along the light transmission direction, the head and tail ends of the two end face couplers are opposite;

[0009] The optical coupling output component is used to output the light emitted from the other end of the component to be tested.

[0010] In some embodiments, the light coupling-injection component includes a light coupling-injection coupler and an incident light waveguide, and the light coupling-injection coupler is connected to the incident light waveguide.

[0011] In some embodiments, the optical coupling input coupler is a grating coupler or an end face coupler;

[0012] And / or, the operating band of the optical coupling input coupler includes one or more of the C band, L band, S band, O band and E band.

[0013] In some embodiments, the light coupling-out component includes a light coupling-out coupler and an outgoing optical waveguide, and the light coupling-out coupler is connected to the outgoing optical waveguide.

[0014] In some embodiments, the optical coupling output coupler is a grating coupler or an end face coupler;

[0015] And / or, the operating band of the optical coupling output coupler includes one or more of the C band, L band, S band, O band and E band.

[0016] In some embodiments, the grating coupler is a converging type, a straight waveguide type, a metasurface type or a photonic crystal type device.

[0017] In some embodiments, the end coupler includes a mode conversion waveguide and a straight waveguide for signal transmission, and one end of the mode conversion waveguide constitutes the head end of the end coupler, and the other end is connected to one end of the straight waveguide, so that the other end of the straight waveguide constitutes the tail end of the end coupler.

[0018] In some embodiments, in the coupler pair, one end of the mode conversion waveguide of one of the end couplers is butted against one end of the mode conversion waveguide of the other end coupler.

[0019] In some embodiments, in the coupler pair, one end of the straight waveguide of one of the end face couplers is butted against one end of the straight waveguide of another end face coupler;

[0020] The optical coupling and incident component includes an end coupler, and one end of the mode conversion waveguide of the end coupler is butted with one end of the mode conversion waveguide of the end coupler in the coupler pair;

[0021] The optical coupling output component includes an end coupler, and one end of the mode conversion waveguide of the end coupler is butted against one end of the mode conversion waveguide of the end coupler in the coupler pair.

[0022] In some embodiments, the end face coupler is a tapered waveguide type, a gradient refractive index type, a multi-tip type, a curved waveguide type, a ridge waveguide type, a groove waveguide type, a tilted angle type, a sub-wavelength type, or a hybrid type device.

[0023] The beneficial effects of the technical solution provided by this application include:

[0024] The present application can eliminate the loss introduced by the coupling interface mode field mismatch, thereby accurately measuring the loss caused by the mode conversion efficiency, thereby realizing the end face coupler mode conversion loss test and process problem location and evaluation, and thus optimizing the end face coupler to obtain an end face coupler with higher coupling efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings required for use in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0026] Figure 1 A schematic diagram of an on-chip end-face coupler test structure provided in one embodiment of the present application;

[0027] Figure 2 for Figure 1 Schematic diagram of the on-chip end coupler test structure during calibration;

[0028] Figure 3 A schematic diagram of an on-chip end-face coupler test structure provided by another embodiment of the present application;

[0029] Figure 4 for Figure 3 Schematic diagram of the on-chip end-face coupler test structure during calibration.

[0030] In the figure: 1, optical coupling incident component; 11, optical coupling incident coupler; 12, incident optical waveguide; 2, optical coupling output component; 21, optical coupling output coupler; 22, output optical waveguide; 3, component to be tested; 4, coupler pair; 5, end coupler; 51, mode conversion waveguide; 52, straight waveguide. DETAILED DESCRIPTION

[0031] In order to make the purpose, technical solution and advantages of the embodiments of the present application clearer, the technical solution in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of this application.

[0032] See also Figure 1 , Figure 2 , Figure 3 and Figure 4 As shown, an embodiment of the present application provides an on-chip end-face coupler test structure, which includes an optical coupling incident component 1 and an optical coupling output component 2. The optical coupling incident component 1 and the optical coupling output component 2 are arranged at intervals along the light transmission direction to form a placement area for the component to be tested 3 therebetween.

[0033] The component under test 3 includes a plurality of coupler pairs 4 cascaded along the light transmission direction, and the coupler pair 4 includes two end face couplers 5 butt-jointedly arranged, and along the light transmission direction, the head and tail ends of the two end face couplers 5 are opposite.

[0034] The light coupling and incident component 1 is used to transmit light from one end of the component to be tested 3 to the component to be tested 3 .

[0035] The optical coupling output component 2 is used to output the light emitted from the other end of the component to be tested 3 .

[0036] The principles of this application are as follows:

[0037] The end coupler 5 generally includes a mode conversion waveguide 51 and a straight waveguide 52 for signal transmission, and one end of the mode conversion waveguide 51 constitutes the head end of the end coupler 5, and the other end is connected to one end of the straight waveguide 52, so that the other end of the straight waveguide 52 constitutes the tail end of the end coupler 5. For ease of understanding, the letters A and B are used to identify them, as shown in FIG. Figure 1As shown, the width of the mode conversion waveguide 51 gradually increases or decreases along the direction of light transmission, so that the width of one end of the mode conversion waveguide 51 is different from that of the other end. For example, the end with a smaller width is recorded as the head end A, and the end with a larger width is connected to the straight waveguide 52, so that the end of the straight waveguide 52 away from the head end A becomes the tail end B.

[0038] Since the two end couplers 5 have opposite ends, in the coupler pair 4, along the light transmission direction, the order of the end coupler 5 is A→B, and the order of the other end coupler 5 is B→A.

[0039] If light first enters the straight waveguide 52 of the first end coupler 5 of the component to be tested 3 through the optical coupling incident component 1, that is, enters from the tail end B of the first end coupler 5, as shown in FIG. Figure 1 As shown, when the transmitted light passes through the first end coupler 5, based on the design principle of the end coupler, under the action of the waveguide, the mode field of the light field is transmitted to the head end A of the first end coupler 5. Since the head and tail ends of the two end couplers 5 are opposite, the head end A of the second end coupler 5 is butted with the head end A of the first end coupler 5. Therefore, the mode field of the head end A of the second end coupler 5 is exactly the same as the mode field of the head end A of the first end coupler 5. No loss is introduced due to the mode field mismatch of the coupling interface. There is only mode conversion loss in the transmission process, and the total loss can be measured. See Figure 2 As shown, before testing the component 3 to be tested or after the test is completed, the optical coupling incident component 1 and the optical coupling output component 2 are directly connected to obtain the test structure body loss caused by the optical coupling incident component 1 and the optical coupling output component 2. The mode conversion loss of the component 3 to be tested can be obtained by deducting the test structure body loss from the above total loss.

[0040] If light first enters the mode conversion waveguide 51 of the first end coupler 5 of the component to be tested 3 through the optical coupling incident component 1, that is, it enters from the head end A of the first end coupler 5, as shown in FIG. Figure 3As shown, when the transmitted light passes through the first end face coupler 5, based on the design principle of the end face coupler, under the action of the waveguide, the mode field of the light field is transmitted to the tail end B of the first end face coupler 5 of the first coupler pair 4, and then transmitted from the tail end B to the head end A of the second end face coupler 5 of the first coupler pair 4. Since the head and tail ends of the two end face couplers 5 are opposite, the head end A of the first end face coupler 5 of the second coupler pair 4 is butt-jointed with the head end A of the second end face coupler 5 of the first coupler pair 4. Therefore, the mode field of the head end A of the first end face coupler 5 of the second coupler pair 4 is exactly the same as the mode field of the head end A of the second end face coupler 5 of the first coupler pair 4. No loss is introduced due to the mode field mismatch of the coupling interface. There is only mode conversion loss in the transmission process, and the total loss can be measured accordingly. See. Figure 4 As shown, before testing the component 3 to be tested or after the test is completed, the optical coupling incident component 1 and the optical coupling output component 2 are directly connected to obtain the test structure body loss caused by the optical coupling incident component 1 and the optical coupling output component 2. The mode conversion loss of the component 3 to be tested can be obtained by deducting the test structure body loss from the above total loss.

[0041] It can be seen from this that the present application can actually eliminate the loss introduced by the coupling interface mode field mismatch, thereby accurately measuring the loss caused by the mode conversion efficiency, thereby realizing the end face coupler mode conversion loss test and process problem location and evaluation, thereby optimizing the end face coupler to obtain an end face coupler with higher coupling efficiency.

[0042] Specifically, at the manufacturing process level, since the mode conversion waveguide has relatively high requirements for the minimum process line width and waveguide sidewall roughness, the loss varies under different process line widths and sidewall roughness, so this test structure can be used to evaluate the process quality. Secondly, the mode conversion efficiency results of this test structure can be used to evaluate the consistency between wafers and wafer batches, so as to provide feedback and adjust the manufacturing process and chip device design.

[0043] It should be noted that when testing, the light emitted by the light source is coupled into the optical coupling input component 1 through the polarization controller through the coupling optical fiber, and then transmitted to the component to be tested 3. After being transmitted through the component to be tested 3, it is coupled out through the optical coupling output component 2 to another output coupling optical fiber, and then transmitted to the optical power meter through the output coupling optical fiber for measurement.

[0044] The component under test 3 in the present application may include one, two, three or more large numbers of coupler pairs 4, so as to achieve wafer-level or chip-level batch testing to evaluate the mode conversion loss of the end-face coupler.

[0045] It can be seen that the test structure provided in this application can not only help engineers locate the process limits of the end coupler more accurately, but also effectively identify specific process defects that may lead to performance degradation, and can systematically analyze and quantify performance changes in each manufacturing batch. Through in-depth analysis of the test data, the key factors affecting the coupling efficiency, such as mode overlap mismatch, material property differences, and slight deviations in the manufacturing process, can be better distinguished. At the same time, based on these test results, the R&D team can adjust and optimize the design parameters and manufacturing processes in a targeted manner, such as improving the waveguide structure design, selecting a more suitable material combination, or optimizing the etching and deposition steps. This not only helps to reduce the uncertainty caused by process fluctuations, but also significantly improves the overall performance and reliability of the end coupling device to achieve higher overall coupling efficiency, ensuring that each end coupler produced can meet the expected optical performance standards, thereby supporting the widespread application of silicon photonic integrated circuits in high-speed communications, sensing and other advanced applications.

[0046] It can be understood that the end face coupler 5 is a device of tapered waveguide type, gradient refractive index type, multi-tip type, curved waveguide type, ridge waveguide type, groove waveguide type, tilt angle type, sub-wavelength type, or hybrid type.

[0047] See also Figure 1 , Figure 2 , Figure 3 and Figure 4 As shown, as a preferred embodiment, the optical coupling incident component 1 includes an optical coupling incident coupler 11 and an incident optical waveguide 12 , and the optical coupling incident coupler 11 is connected to the incident optical waveguide 12 .

[0048] The optical coupling incident coupler 11 is a grating coupler or an end face coupler. If an end face coupler is used, the end face coupler can adopt the same structure as the end face coupler 5 in the component to be tested 3, or can adopt other different existing end face couplers, because no matter whether the same structure as the end face coupler 5 in the component to be tested 3 is adopted, calibration will be performed in the end to eliminate the influence of the optical coupling incident component 1; the grating coupler is a converging type, straight waveguide type, metasurface type or photonic crystal type device.

[0049] The working band of the optical coupling incident coupler 11 includes one or more of the C band, L band, S band, O band and E band.

[0050] See also Figure 1 , Figure 2 , Figure 3 and Figure 4As shown, as a preferred embodiment, the optical coupling output component 2 includes an optical coupling output coupler 21 and an output optical waveguide 22 , and the optical coupling output coupler 21 is connected to the output optical waveguide 22 .

[0051] The optical coupling output coupler 21 is a grating coupler or an end face coupler; the grating coupler is a converging type, a straight waveguide type, a metasurface type or a photonic crystal type device.

[0052] The working band of the optical coupling output coupler 21 includes one or more of the C band, L band, S band, O band and E band.

[0053] As described above, the two end couplers 5 in the coupler pair 4 have opposite ends, and the connection modes of the component to be tested 3 include the following:

[0054] Connection method 1: See Figure 1 As shown, for the coupler pair 4, the head ends A of the two end face couplers 5 are butt-jointed; for two adjacent coupler pairs 4, the tail end B in the end face coupler 5 of one coupler pair 4 is butt-jointed with the tail end B in the end face coupler 5 of the other coupler pair 4.

[0055] For connection mode 1, the optical coupling incident component 1 includes an optical coupling incident coupler 11 and an incident optical waveguide 12, and one end of the incident optical waveguide 12 is connected to the tail end B of the first end face coupler 5 of the component to be tested 3; the optical coupling output component 2 includes an optical coupling output coupler 21 and an output optical waveguide 22, and one end of the output optical waveguide 22 is connected to the tail end B of the last end face coupler 5 of the component to be tested 3.

[0056] If the component under test 3 includes N coupler pairs 4, Figure 1 , the total loss measured is recorded as Q1, such as Figure 2 , the measured test structure body loss is Q2, then the mode conversion loss Q of each end coupler 5 is as follows:

[0057]

[0058] Connection method 2: See Figure 3 As shown, for the coupler pair 4, the tail ends B of the two end face couplers 5 are butt-jointed; for two adjacent coupler pairs 4, the head end A in the end face coupler 5 of one coupler pair 4 is butt-jointed with the head end A in the end face coupler 5 of the other coupler pair 4.

[0059] For the second connection mode, in addition to the optical coupling incident coupler 11 and the incident optical waveguide 12, the optical coupling incident component 1 also needs to add an end face coupler 5, and the head end A of the end face coupler 5 is connected to the head end A of the first end face coupler 5 of the component to be tested 3; in addition to the optical coupling output coupler 21 and the output optical waveguide 22, the optical coupling output component 2 also needs to add an end face coupler 5, and the head end A of the end face coupler 5 is connected to the head end A of the last end face coupler 5 of the component to be tested 3.

[0060] If the component under test 3 includes N coupler pairs 4, Figure 3 , the total loss measured is recorded as Q1, such as Figure 4 , the measured test structure body loss is Q2, then the mode conversion loss Q of each end coupler 5 is as follows:

[0061]

[0062] It can be understood that, for the second connection mode, the end face coupler 5 added to the optical coupling incident component 1 and the optical coupling output component 2 can be a common end face coupler 5, that is, it can be used for different components 3 to be tested.

[0063] It can be understood that, for the above connection mode 2, since the number N of the above coupler pairs 4 can be very large when batch testing is performed, at this time, two end face couplers 5 can be directly extracted from the original component to be tested 3 and allocated to the optical coupling incident component 1 and the optical coupling output component 2, and the remaining coupler pairs 4 are used as the component to be tested 3 actually measured. At this time, the calculation formula of the mode conversion loss Q is as follows:

[0064]

[0065] Wherein, N is the number of coupler pairs 4 included in the component under test 3, such as Figure 3 , the total loss measured is recorded as Q1, such as Figure 4 , the measured test structure body loss is Q2.

[0066] The reason why this connection method 2 can be used is that when two coupled end face couplers 5 are connected to form a coupler pair 4, there is no need to identify the faces. Whether the head end is to the head end or the tail end is to the tail end, the test structure provided by the present application can be used for testing, which plays a fool-proof design. This is because: since the mode conversion loss Q is a calculated average value, and the number N can be very large, the lack of one coupler pair 4 (i.e., N-1) will not have much impact, and the accuracy of the results can also be guaranteed.

[0067] In the description of the present application, it should be noted that the terms "upper", "lower", etc. indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present application and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present application. Unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be an indirect connection through an intermediate medium, or it can be a connection between the two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the present application can be understood according to the specific circumstances.

[0068] It should be noted that, in this application, relational terms such as "first" and "second" are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, the elements defined by the sentence "comprise a ..." do not exclude the presence of other identical elements in the process, method, article or device including the elements.

[0069] The above description is only a specific implementation of the present application, so that those skilled in the art can understand or implement the present application. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present application. Therefore, the present application will not be limited to the embodiments shown herein, but will conform to the widest range consistent with the principles and novel features applied for herein.

Claims

1. An on-chip end-face coupler test structure, characterized in that: It includes: An optical coupling incident component (1) is used to transmit light from one end of a component to be tested (3) to the component to be tested (3), wherein the component to be tested (3) comprises a plurality of coupler pairs (4) cascaded along a light transmission direction, the coupler pair (4) comprises two end face couplers (5) butt-jointedly arranged, and along the light transmission direction, the head and tail ends of the two end face couplers (5) are opposite; The light coupling output component (2) is used to output the light emitted from the other end of the component to be tested (3).

2. The on-chip end-face coupler test structure according to claim 1, characterized in that: The optical coupling incident component (1) comprises an optical coupling incident coupler (11) and an incident optical waveguide (12), wherein the optical coupling incident coupler (11) is connected to the incident optical waveguide (12).

3. The on-chip end-face coupler test structure according to claim 2, characterized in that: The optical coupling input coupler (11) is a grating coupler or an end face coupler; And / or, the working band of the optical coupling input coupler (11) includes one or more of the C band, L band, S band, O band and E band.

4. The on-chip end-face coupler test structure according to claim 1, characterized in that: The optical coupling output component (2) comprises an optical coupling output coupler (21) and an output optical waveguide (22), wherein the optical coupling output coupler (21) is connected to the output optical waveguide (22).

5. The on-chip end-face coupler test structure according to claim 4, characterized in that: The optical coupling output coupler (21) is a grating coupler or an end face coupler; And / or, the operating band of the optical coupling output coupler (21) includes one or more of the C band, L band, S band, O band and E band.

6. The on-chip end-face coupler test structure according to claim 3 or 5, characterized in that: The grating coupler is a converging type, a straight waveguide type, a metasurface type or a photonic crystal type device.

7. The on-chip end-face coupler test structure according to claim 1, characterized in that: The end face coupler (5) comprises a mode conversion waveguide (51) and a straight waveguide (52) for signal transmission, and one end of the mode conversion waveguide (51) constitutes the head end of the end face coupler (5), and the other end is connected to one end of the straight waveguide (52), so that the other end of the straight waveguide (52) constitutes the tail end of the end face coupler (5).

8. The on-chip end-face coupler test structure according to claim 7, characterized in that: In the coupler pair (4), one end of the mode conversion waveguide (51) of one of the end face couplers (5) is butted against one end of the mode conversion waveguide (51) of the other end face coupler (5).

9. The on-chip end-face coupler test structure according to claim 7, characterized in that: In the coupler pair (4), one end of the straight waveguide (52) of one of the end face couplers (5) is butted against one end of the straight waveguide (52) of the other end face coupler (5); The optical coupling incident component (1) comprises an end face coupler (5), and one end of a mode conversion waveguide (51) of the end face coupler (5) is butted against one end of a mode conversion waveguide (51) of the end face coupler (5) in the coupler pair (4); The optical coupling output component (2) comprises an end face coupler (5), and one end of a mode conversion waveguide (51) of the end face coupler (5) is butted against one end of a mode conversion waveguide (51) of the end face coupler (5) in the coupler pair (4).

10. The on-chip end-face coupler test structure according to claim 1, characterized in that: The end face coupler (5) is a device of a tapered waveguide type, a gradient refractive index type, a multi-tip type, a curved waveguide type, a ridge waveguide type, a groove waveguide type, a tilt angle type, a sub-wavelength type, or a hybrid type.

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