Optical chip-optical fiber coupler based on collimating grating penetrating through substrate

Abstract

The invention discloses an optical chip-optical fiber coupler based on a collimating grating penetrating through a substrate, which belongs to the technical field of photoelectric chips and comprises a substrate, an inverted optical chip is arranged on the substrate, and the optical chip comprises at least one optical device, an optical waveguide array for realizing input and output and a collimating grating array. The collimating grating array is provided with a gradually changing period and duty ratio, so that light output from the optical waveguide array is diffracted to the substrate through the collimating grating array and is propagated to the back surface of the optical chip as basically collimated light; an optical coupling element array is arranged at the position, corresponding to emergent light of the collimating grating array, of the back face of the optical chip to couple light to an optical fiber array. By the adoption of the structure, high-efficiency coupling of the optical chip and the optical fiber array is achieved, and compared with a common grating coupler and an edge coupler, the coupler has higher coupling efficiency and alignment tolerance, is easier to manufacture and can be widely applied to the fields of optical IO, photoelectric sealing (CPO) and the like of large-scale photoelectric integrated chips.

Description

Technical Field

[0001] The invention relates to the technical field of optoelectronic chips, and in particular to an optical chip-fiber coupler based on a penetrating substrate collimating grating. Background Art

[0002] Current data centers / intelligent computing systems are composed of tens of thousands of servers connected by fiber optic networks. With the exponential growth of switching bandwidth, pluggable optical modules will gradually be replaced by co-packaged optics (CPO). CPO co-packages multiple optical chips and electrical chips on a substrate, reducing the RF loss between optoelectronic chips, improving signal quality, and significantly increasing system integration and edge switching bandwidth density. However, the number of optical fibers in the optical interface of CPO has increased significantly, and the coupling complexity from optical chips to fiber arrays has increased significantly, making it increasingly difficult for traditional optical connectors that rely on fiber array jumpers (such as MPO) to carry them. In order to meet the ultra-high-density fiber connection requirements of CPO, the industry has begun to study new optical interfaces in which optical connectors are directly coupled to optical chips while still being pluggable. However, existing technical solutions all have problems with high process difficulty and low precision and fault tolerance.

[0003] For example, in the document Detachable Optical Chiplet Connector for Co-Packaged Photonics, Intel proposed to use glass to make an optical bridge interface and integrate it with the silicon photonic chip to couple the light out of the silicon photonic chip. The optical bridge interface has a passive alignment structure, and the fiber array has a matching passive alignment structure, which can be directly passively aligned and coupled when inserted, and is fixed by a mechanical structure, with an average coupling loss of 1.41dB. The glass bridge interface of this solution is difficult to make and has a high cost.

[0004] In patent US20230251428A1, Broadcom proposed to attach a lens array to the light-emitting side of the silicon photonic chip and the end face of the fiber array for coupling, and rely on an external mechanical structure to achieve passive alignment when the fiber array is inserted. This solution attaches a lens to the light-emitting side of the chip, which requires high process precision and a small end face coupling alignment tolerance.

[0005] In the document Detachable interface toward a low-loss reflow-compatible fiber coupling for co-packaged optics (CPO), XuChuang proposed using two microlens arrays in two mating connectors for coupling. The two mating connectors are placed on the substrate and in front of the fiber array respectively. This solution can achieve a coupling loss of less than 1 dB. This solution is close to the traditional coupling principle, but has a complex process, a small end face coupling alignment tolerance, and a large overall size. Summary of the invention

[0006] The purpose of the present invention is to provide an optical chip-fiber coupler based on a penetrating substrate collimating grating, corresponding to an optical interface, and proposes a penetrating substrate chirped collimating grating for coupling optical fiber to an optical chip. The grating is used together with a total reflection microprism and a microlens array to collimate all light beams into parallel light for coupling, thereby solving the problems of low efficiency and small alignment tolerance of ordinary grating coupling or end face coupling. The optical interface based on this enables the optical fiber array to be pluggable and efficiently coupled to the optical chip. By coupling the light out from the back of the optical chip, the optical device layout of the optical chip is not restricted by the position of the light outlet and the electrical interface when the optical chip is flipped and fanned out on the substrate, and can be freely arranged into a two-dimensional array, thereby improving the edge density of the optical chip coupled optical fiber and the integration of the optical chip.

[0007] To achieve the above-mentioned purpose, the present invention provides an optical chip-fiber coupler based on a substrate-penetrating collimating grating, comprising a substrate, on which a flip-mounted optical chip is arranged, wherein the optical chip comprises at least one optical device, an optical waveguide array for realizing input and output, and a collimating grating array, wherein the collimating grating array is provided with a gradually varying period and duty cycle so that the light output from the optical waveguide array is diffracted toward the substrate through the collimating grating array, and propagates to the back side of the optical chip as substantially collimated light, and an optical coupling element array is arranged at a position on the back side of the optical chip corresponding to the output light of the collimating grating array to couple the light to an optical fiber array.

[0008] Preferably, the optical coupling element array includes a total reflection microprism and a microlens array arranged on the output light path of the total reflection microprism, and the microlens array corresponds to the optical fiber array and is arranged as a single unit or a one-dimensional array or a two-dimensional array.

[0009] Preferably, the material of the substrate is Si or quartz or glass or ceramic or organic material, a plurality of electrical chips are arranged on the substrate, and the optical coupling element array and the optical fiber array are connected to the substrate via a mechanical structure.

[0010] Preferably, the mechanical structure includes a fiber optic connector arranged on the outside of the fiber optic array and an optical interface seat on the substrate, the fiber optic connector being movably connected to the optical interface seat, and when the fiber optic connector is inserted, the position error of the fiber optic array meets the tolerance of coupling with the collimating grating array.

[0011] Preferably, the optical chip material is set to InP or SOI or SiN or thin film lithium niobate, the types of optical devices include lasers, optical amplifiers, optical modulators, optical detectors, multiplexers / demultiplexers, and the back of the optical chip substrate is coated with an optical anti-reflection film.

[0012] Preferably, the structure of the collimating grating array is set as a one-dimensional array or a two-dimensional array, and the collimating grating array is specifically a chirped grating. A gradual grating coupling coefficient is obtained by optimizing the design of the grating etching depth and the gradual duty cycle, so that the coupled outgoing or incident light has a certain light field distribution.

[0013] Preferably, a layer of metal high-reflection film is deposited on the surface of the upper cladding of the collimating grating array as a metal reflector, and the distance between the metal high-reflection film and the collimating grating is adjusted so that the light diffracted from the collimating grating array to the upper cladding and reflected by the metal high-reflection film and then penetrating the collimating grating array interferes constructively with the light diffracted directly to the substrate by the collimating grating array.

[0014] Preferably, the material of the total reflection microprism is Si or quartz or glass, the reflection surface of the total reflection microprism is arranged at the hypotenuse and totally reflects the light, and the angle of the hypotenuse satisfies the requirement of redirecting the outgoing light of the collimated grating array into the direction of the parallel optical chip plane and aligning it with the optical fiber array; the two right-angled edges of the total reflection microprism are coated with an optical anti-reflection film, and the projection area of ​​the total reflection microprism along the propagation direction of the light beam covers the collimated grating array.

[0015] Preferably, the microlens array is mounted on the end face of the optical fiber array or is arranged on a total reflection microprism, and the microlens array focuses and couples the collimated light emitted by the optical chip to the optical fiber array.

[0016] Preferably, the microlens array is integrally fabricated on the back side of the optical chip substrate, and the microlens array focuses and couples the collimated light emitted by the optical chip to the optical fiber array.

[0017] Therefore, the present invention adopts the above-mentioned optical chip-fiber coupler based on penetrating substrate collimating grating, which has the following advantages:

[0018] The optical chip-fiber coupler based on the penetrating substrate collimating grating proposed by the present invention collimates the outgoing / incoming light of the optical chip into parallel light coupling with a large light spot, which significantly improves the coupling efficiency and alignment tolerance compared with ordinary grating coupling and edge coupling, relaxes the mechanical positioning accuracy requirements of the pluggable coupling of the fiber array, and makes the pluggable optical interface of the fiber easy to realize. Moreover, the optical coupler of the present invention can adopt a two-dimensional collimating grating array and a two-dimensional fiber array, thereby significantly improving the edge density of the optical chip coupling optical fiber. In addition, the penetrating substrate collimating grating allows light to be input / output from the back of the optical chip, and the electrical interface of the optical chip is on the front of the chip. The two will not affect each other in space, and then the optical chip can be flipped on the substrate without being restricted by the position of the light outlet to make a fan-out package, so that the optical device of the optical chip can also be free from the constraints of the position of the light outlet and the position of the electrical interface, and can be freely arranged into a two-dimensional array, thereby improving the integration of the optical chip. Optical chip application The optical chip-fiber coupler and optical interface based on the penetrating substrate collimating grating of the present invention can simplify the complex optical coupling packaging process, which is convenient for its application in the fields of optical IO, CPO, etc.

[0019] The technical solution of the present invention is further described in detail below through the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 It is a cross-sectional view of the first embodiment of an optical chip-fiber coupler based on a penetrating substrate collimating grating of the present invention;

[0021] Figure 2 This is a schematic diagram of a top view of the structure of an optical chip in Embodiment 1 of an optical chip-fiber coupler based on a penetrating substrate collimating grating according to the present invention;

[0022] Figure 3 A schematic diagram of the collimated light coupling optical path in Embodiment 1 of an optical chip-fiber coupler based on a penetrating substrate collimating grating according to the present invention;

[0023] Figure 4 This is a schematic diagram of a pluggable coupling process in an optical chip-fiber coupler based on a penetrating substrate collimating grating according to the present invention. Figure 4 (a) is a schematic diagram before installation. Figure 4 (b) is a schematic diagram after installation;

[0024] Figure 5 A schematic diagram of an optical interface array of an optical chip-fiber coupler based on a penetrating substrate collimating grating according to the present invention;

[0025] Figure 6 It is a schematic diagram of a second embodiment of an optical chip-fiber coupler based on a penetrating substrate collimating grating according to the present invention;

[0026] Figure 7It is a schematic diagram of a third embodiment of an optical chip-fiber coupler based on a penetrating substrate collimating grating according to the present invention;

[0027] Figure numerals: 100, optical chip; 101, collimating grating array; 102, optical waveguide; 103, optical device; 104, metal reflector; 105, substrate; 200, total reflection microprism; 300, optical fiber connector; 301, optical fiber array; 302, microlens array; 400, optical interface seat; 500, substrate; 501, electrical chip. DETAILED DESCRIPTION

[0028] In order to make the purpose, technical solutions and advantages of the embodiments 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 in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. The components of the embodiments of the present invention described and shown in the drawings here can be arranged and designed in various different configurations. The specific model specifications need to be selected and determined according to the actual specifications of the device, and the specific selection calculation structure adopts the existing technology in the field, so it will not be described in detail.

[0029] Embodiment 1

[0030] like Figure 1-Figure 5 As shown, the present invention provides an optical chip-fiber coupler based on a penetrating substrate collimating grating, specifically as Figure 1 As shown, it includes an optical chip 100, a total reflection microprism 200, an optical fiber connector 300, an optical interface seat 400, a substrate 500, and an electrical chip 501. The optical chip 100 is made of a collimating grating array 101, an optical waveguide 102, an optical device 103, a metal reflector 104, and a substrate 105, and the optical fiber connector 300 is made of an optical fiber array 301 and a microlens array 302.

[0031] A collimating grating array 101 is fabricated inside the optical chip 100. The optical chip 100 may be made of InP, SOI, SiN, thin film lithium niobate (TFLN), etc. The optical chip 100 includes an optical waveguide 102 and at least one of optical devices 103 such as a laser, an optical amplifier, an optical modulator, an optical detector, and a multiplexer / demultiplexer. The collimating grating array 101 is connected to these optical devices through the optical waveguide 102. The specific connection method is as follows: Figure 2 As shown, the light output from the output optical waveguide 102 is diffracted by the collimating grating array 101 to become collimated light, and then penetrates the substrate 105 to propagate to the back of the optical chip 100. In order to reduce the reflection of the optical chip 100 from the back, the back of the optical chip 100 is coated with an optical anti-reflection film.

[0032] The collimating grating array 101 is designed as a chirped collimating grating array by apodization, and the grating etching depth and the gradually changing duty cycle are optimized to obtain the gradually changing grating coupling coefficient so that the light input and output gratings have a certain light field distribution, the spot size is large and collimated, so that a large alignment tolerance can be obtained, and passive alignment can be used. The collimating grating can be arranged as a one-dimensional array or a two-dimensional array to meet the requirements of the number of input / output ports of the optical chip 100.

[0033] Because the grating diffraction will inevitably emit toward the front of the optical chip 100, a layer of metal high-reflection film is deposited on the front of the optical chip 100 as a metal reflector 104, thereby avoiding the more complicated process of the stepped blazed grating tooth surface that requires two-step etching, and improving the diffraction directionality and efficiency of emission from the back. The metal reflector 104 is at a certain distance from the collimating grating array 101, so that the light emitted from the back directly diffracted by the collimating grating array 101 and the light diffracted above the collimating grating array 101 and then reflected by the metal reflector 104 and emitted from the back can be constructively coherent, making the collimating grating array 101 emit the strongest light, thereby improving the coupling efficiency of the emitted light. Similarly, a metal reflector 104 can be set at the receiving end so that the incident light received by the collimating grating array 101 is the strongest, thereby improving the coupling efficiency of the received light.

[0034] The total reflection microprism 200 is attached to the back of the optical chip 100 at the position facing the collimating grating array 101. The hypotenuse of the total reflection microprism 200 reflects the incident light, and turns the collimated light propagating to the back of the optical chip into collimated light propagating parallel to the plane of the optical chip, and aligns with the optical fiber array 301. Therefore, the hypotenuse angle of the total reflection microprism 200 is determined according to the exit angle of the collimating grating 101. The two right-angled edges of the total reflection microprism 200 are coated with optical anti-reflection film to reduce reflection. The size of the total reflection microprism 200 is to cover the entire grating array. The material of the total reflection microprism 200 can be Si, quartz, glass, etc.

[0035] In this embodiment, the optical fiber array 301 and the collimating grating array 101 are set to have the same spacing. The optical fiber array 301 can be a single unit or a one-dimensional array, or a two-dimensional array, which is specifically determined by the collimating grating array 101. The number of optical fibers in the optical fiber array is determined by the number of collimating grating arrays 101.

[0036] According to the above content, the optical chip-fiber coupling optical path in this embodiment is as follows Figure 3As shown, the working direction of the optical path includes forward and reverse directions. When the optical fiber connector 300 is inserted into the optical interface seat 400, the light output from the output optical waveguide 102 array of the optical chip 100 is first diffracted into collimated light by the collimating grating array 101, penetrates the substrate 105 and propagates to the back of the optical chip 100, and then passes through the total reflection right-angle prism 200 to be turned into collimated light propagating parallel to the plane of the optical chip, and is aligned with the optical fiber array 301. Finally, the microlens array 302 focuses the collimated light and couples it to the optical fiber array 301; similarly, when working in the reverse direction, the light is emitted from the optical fiber array 301, collimated by the microlens array 302, reflected by the total reflection microprism 200 on the back of the chip, and then penetrates the substrate 105 to be incident on the collimating grating array 101 of the optical chip 100, and then diffracted by the grating array to be coupled to the input optical waveguide 102 of the optical chip 100.

[0037] The optical interface seat 400 is mounted on the substrate 500 that packages the optical chip 100, so that the optical fiber array 301 can be flexibly plugged in or fixed on the substrate through the optical fiber connector 300. Figure 4 As shown, when the optical fiber connector 300 is inserted, it is precisely fixed so that its position error satisfies the alignment tolerance of the collimated light emitted by the collimating grating array 101 coupled to the optical fiber connector 300 .

[0038] The substrate 500 can allow the optical chip 100 to be flipped on it for fan-out packaging, so that various optical devices of the optical chip can be arranged in a two-dimensional array. The substrate 500 can package the electrical chip 501 and the optical chip 100 together. The material of the substrate 500 can be Si, glass, ceramics, and organic materials, etc., and the substrate 500 can be packaged in multiple and multi-layer stacks to obtain the best overall optoelectronic performance.

[0039] The fiber optic pluggable optical interface can be packaged in multiple pieces on a larger substrate 502 or PCB to form an array such as Figure 5 As shown, it is used in application scenarios such as CPO.

[0040] Embodiment 2:

[0041] The microlens array 302 in the first embodiment can be integrated with the total reflection microprism 200. Figure 6As shown, the end face of the optical fiber array 301 of the optical connector 300 is no longer attached with the microlens array 302. In this embodiment, when the optical fiber connector 300 is inserted into the optical interface seat 400, the light output from the output optical waveguide 102 array of the optical chip 100 is first diffracted into collimated light by the collimating grating array 101, penetrates the substrate 105 and propagates to the back of the optical chip 100, and then is reflected by the hypotenuse of the total reflection prism 200 and turned into collimated light propagating parallel to the plane of the optical chip, and when it is emitted from the total reflection microprism 200, it is focused and coupled to the optical fiber array 301 by the microlens array 302 on the surface; similarly, when working in the reverse direction, the light is emitted from the optical fiber array 301 to the microlens array 302 on the surface of the total reflection microprism 200 and collimated, and then after being reflected by the total reflection microprism 200, it penetrates the substrate 105 and is incident on the collimating grating array 101 of the optical chip 100, and then is diffracted and coupled to the input optical waveguide 102 of the optical chip 100 by the grating array. The optical fiber array 301 and the microlens array 302 may be a unit, a one-dimensional linear array or a two-dimensional plane array.

[0042] Embodiment 3

[0043] The microlens array 302 in the first embodiment is attached to the back of the optical chip 100 at the position of the alignment grating array 101. The internal structure is as follows: Figure 7 As shown, in this embodiment, the optical chip 100 and the optical fiber array 301 are set to a vertical coupling geometric relationship, and there is no need to set up an additional total reflection microprism. The light output from the optical chip 100 from the output optical waveguide 102 array is first diffracted by the collimating grating array 101 into collimated light, penetrates the substrate 105 and propagates to the back of the optical chip 100, and then is focused and coupled to the optical fiber array 301 through the microlens array 302; similarly, when working in the reverse direction, the light is emitted from the optical fiber array 301 to the microlens array 302 and is collimated, penetrates the substrate 105 and is incident on the collimating grating array 101 of the optical chip 100, and then is diffracted and coupled to the input optical waveguide 102 of the optical chip 100 through the grating array, wherein the optical fiber array 301 and the microlens array 302 can be a unit, a one-dimensional linear array or a two-dimensional plane array.

[0044] Therefore, the present invention adopts an optical chip-fiber coupler based on a penetrating substrate collimating grating, and proposes a penetrating substrate chirped collimating grating for coupling optical fiber to optical chip. The collimating grating is used together with a total reflection microprism and a microlens array to collimate all light beams into parallel light for coupling, thereby solving the problems of low efficiency and small alignment tolerance of ordinary grating coupling or end face coupling. The optical interface based on this enables the optical fiber array to be pluggable and efficiently coupled to the optical chip. By coupling the light out from the back of the optical chip, the optical device layout of the optical chip is not restricted by the position of the light outlet and the electrical interface when the optical chip is flipped and fanned out on the substrate, and can be freely arranged into a two-dimensional array, thereby improving the edge density of the optical chip coupled optical fiber and the integration of the optical chip.

[0045] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that they can still modify or replace the technical solution of the present invention with equivalents, and these modifications or equivalent replacements cannot cause the modified technical solution to deviate from the spirit and scope of the technical solution of the present invention.

Claims

1. An optical chip-fiber coupler based on a penetrating substrate collimating grating, characterized in that: The invention comprises a substrate, on which a flip-chip optical chip is arranged, wherein the optical chip comprises at least one optical device, an optical waveguide array for realizing input and output, and a collimating grating array, wherein the collimating grating array is provided with a gradual period and duty cycle so that the light output from the optical waveguide array is diffracted toward the substrate through the collimating grating array and propagates to the back side of the optical chip as substantially collimated light, and an optical coupling element array is arranged at a position on the back side of the optical chip corresponding to the output light of the collimating grating array to couple the light to an optical fiber array.

2. The optical chip-fiber coupler based on a through-substrate collimated grating according to claim 1, characterized in that: The optical coupling element array includes a total reflection microprism and a microlens array arranged on the outgoing light path of the total reflection microprism. The microlens array corresponds to the optical fiber array and is arranged as a single unit or a one-dimensional array or a two-dimensional array.

3. The optical chip-fiber coupler based on a through-substrate collimated grating according to claim 1, characterized in that: The material of the substrate is Si, quartz, glass, ceramic or organic material. A plurality of electrical chips are arranged on the substrate. The optical coupling element array and the optical fiber array are connected to the substrate through a mechanical structure.

4. The optical chip-fiber coupler based on a through-substrate collimated grating according to claim 3, characterized in that: The mechanical structure includes an optical fiber connector arranged outside the optical fiber array and an optical interface seat on a substrate. The optical fiber connector is movably connected to the optical interface seat. When the optical fiber connector is inserted, the position error of the optical fiber array meets the tolerance of coupling with the collimating grating array.

5. The optical chip-fiber coupler based on a through-substrate collimated grating according to claim 1, characterized in that: The optical chip material is set to InP or SOI or SiN or thin film lithium niobate, the types of optical devices include lasers, optical amplifiers, optical modulators, optical detectors, multiplexers / demultiplexers, and the back of the optical chip substrate is coated with an optical anti-reflection film.

6. The optical chip-fiber coupler based on a through-substrate collimated grating according to claim 1, characterized in that: The structure of the collimating grating array is set as a one-dimensional array or a two-dimensional array. The collimating grating array is specifically a chirped grating. The gradient grating coupling coefficient is obtained by optimizing the design of the grating etching depth and the gradient duty cycle, so that the coupled outgoing or incident light has a certain light field distribution.

7. The optical chip-fiber coupler based on a through-substrate collimated grating according to claim 1, characterized in that: A layer of metal high-reflection film is deposited on the upper cladding surface of the collimating grating array as a metal reflector, and the distance between the metal high-reflection film and the collimating grating is adjusted so that the light diffracted from the collimating grating array to the upper cladding and reflected by the metal high-reflection film and then penetrating the collimating grating array interferes constructively with the light diffracted directly to the substrate by the collimating grating array.

8. The optical chip-fiber coupler based on a through-substrate collimated grating according to claim 2, characterized in that: The material of the total reflection microprism is Si or quartz or glass. The reflection surface of the total reflection microprism is arranged at the hypotenuse and totally reflects the light. The angle of the hypotenuse satisfies the requirement of redirecting the outgoing light of the collimated grating array into the direction of the parallel light chip plane and aligning it with the optical fiber array. The two right-angled edges of the total reflection microprism are coated with optical anti-reflection films, and the projection area of ​​the total reflection microprism along the propagation direction of the light beam covers the collimated grating array.

9. The optical chip-fiber coupler based on a through-substrate collimated grating according to claim 2, characterized in that: The microlens array is mounted on the end face of the optical fiber array or arranged on a total reflection microprism, and the microlens array focuses and couples the collimated light emitted by the optical chip to the optical fiber array.

10. The optical chip-fiber coupler based on a through-substrate collimated grating according to claim 2, characterized in that: The microlens array is integrally manufactured on the back of the optical chip substrate, and the microlens array focuses and couples the collimated light emitted by the optical chip to the optical fiber array.

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