An optical chip-fiber coupler based on a penetrating substrate collimating grating

Abstract

The present invention discloses an optical chip-fiber coupler based on a penetrating substrate collimating grating. This optical chip coupler belongs to the technical field of optoelectronic chips and includes a substrate on which a flip-chip optical chip is mounted. The optical chip includes at least one optical device, an optical waveguide array for input and output, and a collimating grating array. The collimating grating array is configured with a gradually varying period and duty cycle so that light output from the optical waveguide array is diffracted toward the substrate through the collimating grating array and propagates as substantially collimated light to the back of the optical chip. An optical coupling element array is provided on the back of the optical chip at positions corresponding to the output light from the collimating grating array to couple the light to an optical fiber array. The present invention utilizes this structure to achieve high-efficiency coupling between the optical chip and the optical fiber array. Compared to conventional grating couplers and edge couplers, the present invention has higher coupling efficiency and alignment tolerance, is easier to manufacture, and can be widely used in optical I / O and combined optoelectronic packaging (CPO) for large-scale optoelectronic integrated chips.

Description

Technical Field

[0001] The present 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 packages multiple optical chips and electrical chips together 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 difficult for traditional optical connectors (such as MPO) that rely on fiber array jumpers to carry the load. In order to meet the ultra-high-density fiber connection of CPO, the industry has begun to study a new type of optical interface in which the optical connector is directly coupled to the optical chip while the optical connector is still pluggable. However, the existing technical solutions have problems with high process difficulty and low precision fault tolerance.

[0003] For example, in the paper "Detachable Optical Chiplet Connector for Co-Packaged Photonics," Intel proposes using glass to create an optical bridge interface integrated with a silicon photonics chip to couple light out of the chip. The optical bridge interface features a passive alignment structure, and the fiber array has a matching passive alignment structure, enabling direct passive alignment and coupling during insertion. The structure is secured by a mechanical structure, resulting in an average coupling loss of 1.41 dB. This solution presents significant challenges and high costs in manufacturing the glass bridge interface.

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

[0005] In the paper "Detachable interface toward a low-loss reflow-compatible fiber coupling for co-packaged optics (CPO)," Innolight proposes coupling using two microlens arrays housed in two mating connectors, one on the substrate and one in front of the fiber array. This solution can achieve a coupling loss of less than 1 dB. While similar to traditional coupling principles, this approach has complex manufacturing processes, limited end-face coupling alignment tolerance, and a larger 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 fibers to optical chips. This grating is used together with a total reflection microprism and a microlens array to collimate all light beams into parallel light for coupling, 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 fiber array to be pluggable and efficiently coupled to the optical chip. By allowing the optical chip to couple light from the back side, the optical chip can be flipped and fanned out on the substrate. The optical device layout of the optical chip is not restricted by the position of the light output port and the electrical interface, 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 objectives, the present invention provides an optical chip-to-fiber coupler based on a penetrating substrate collimating grating. The optical chip comprises a substrate on which a flip-chip optical chip is mounted. The optical chip includes at least one optical device, an optical waveguide array for input and output, and a collimating grating array. The collimating grating array is configured with a gradually varying period and duty cycle so that light output from the optical waveguide array is diffracted toward the substrate through the collimating grating array and propagates as substantially collimated light to the back side of the optical chip. An optical coupling element array is disposed on the back side of the optical chip at a position corresponding to the output light from the collimating grating array to couple the light to a 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 substrate is made of Si, quartz, glass, ceramic, or organic material, a plurality of electrical chips are provided 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 an optical fiber connector arranged on the outside of the optical fiber array and an optical interface seat on the substrate, and 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.

[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. By optimizing the design of the grating etching depth and the gradual duty cycle, a gradual grating coupling coefficient is obtained, 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 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 toward the upper cladding and reflected by the metal high-reflection film and then penetrates the collimating grating array interferes constructively with the light diffracted directly toward the substrate by the collimating grating array.

[0014] Preferably, the material of the total reflection microprism is Si, quartz or glass, the reflective 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 collimating 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 projected area of ​​the total reflection microprism along the propagation direction of the light beam covers the collimating 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 to ordinary grating coupling and edge coupling, relaxes the mechanical positioning accuracy requirements of the pluggable coupling of the fiber array, and makes the pluggable fiber optical interface 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 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 flip-chip mounted on the substrate for fan-out packaging without being restricted by the position of the light outlet. As a result, the optical components of the optical chip can also be freely arranged into a two-dimensional array without being constrained by the position of the light outlet and the position of the electrical interface, thereby improving the integration of the optical chip. The optical chip application of 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, facilitating 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 This is a cross-sectional view of a first embodiment of an optical chip-fiber coupler based on a penetrating substrate collimating grating according to the present invention;

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

[0022] Figure 3 Schematic diagram of the collimated light coupling optical path in Example 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 the 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 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 7Schematic 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 generally 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 based on the actual specifications of the device, and the specific selection calculation structure adopts the existing technology in this field, so it will not be described in detail.

[0029] Example 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 electronic chip 501. The optical chip 100 includes a collimating grating array 101, an optical waveguide 102, an optical device 103, a metal reflector 104, and a substrate 105. The optical fiber connector 300 includes 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 can 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 the 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 via 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, which then penetrates the substrate 105 and propagates to the back of the optical chip 100. To reduce reflection from the back of the optical chip 100, 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 through apodization. Optimizing the grating etch depth and gradually varying the duty cycle yields a gradually varying grating coupling coefficient. This results in a uniform light field distribution for the light entering and exiting the gratings, a large, collimated spot size, and a wide alignment tolerance, enabling passive alignment. The collimating gratings can be arranged in a one- or two-dimensional array to meet the required number of input / output ports on the optical chip 100.

[0033] Because grating diffraction will inevitably be emitted 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 complex process of requiring two-step etching of the stepped blazed grating tooth surface, 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 directly diffracted by the collimating grating array 101 and emitted from the back 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 light emitted from the collimating grating array 101 the strongest, thereby improving the coupling efficiency of the emitted light. Similarly, a metal reflector 104 can be set at the receiving end to make the incident light received by the collimating grating array 101 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, directly opposite the collimating grating array 101. The hypotenuse of the total reflection microprism 200 reflects the incident light, redirecting the collimated light propagating to the back of the optical chip into collimated light propagating parallel to the plane of the optical chip and aligning it with the optical fiber array 301. Therefore, the hypotenuse angle of the total reflection microprism 200 is determined by the output angle of the collimating grating 101. The two right-angled edges of the total reflection microprism 200 are coated with an optical anti-reflection coating to reduce reflection. The size of the total reflection microprism 200 is designed 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 directions of the optical path include 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 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 and 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, allowing the optical fiber array 301 to 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 meets the alignment tolerance of the collimating grating array 101 coupling the collimated light emitted from the optical fiber connector 300.

[0038] The substrate 500 allows the optical chip 100 to be flip-chip mounted on it for fan-out packaging, enabling a two-dimensional array arrangement of the various optical components within the optical chip. The substrate 500 can co-package the electrical chip 501 and the optical chip 100. Substrate 500 can be made of materials such as silicon (Si), glass, ceramic, and organic materials, and multiple layers of substrate 500 can be stacked for optimal overall optoelectronic performance.

[0039] Multiple optical fiber pluggable optical interfaces can be packaged 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] Example 2:

[0041] The micro lens array 302 in the first embodiment can be integrated with the total reflection micro prism 200, as shown in FIG. 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 by the collimating grating array 101 into collimated light, penetrates the substrate 105 and propagates to the back of the optical chip 100, 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. 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 emitted from the optical fiber array 301 is collimated by the microlens array 302 on the surface of the total reflection microprism 200, then reflected by the total reflection microprism 200, penetrates the substrate 105, and is incident on the collimating grating array 101 of the optical chip 100. It is then diffracted by the grating array and coupled to the input optical waveguide 102 of the optical chip 100. The optical fiber array 301 and the microlens array 302 can be a unit, a one-dimensional linear array, or a two-dimensional planar array.

[0042] Example 3

[0043] The micro lens 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 arranged in a vertically coupled geometric relationship, and no additional total reflection microprism is required. 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 is then focused and coupled to the optical fiber array 301 by the microlens array 302. Similarly, when working in the reverse direction, the light is emitted from the optical fiber array 301, is collimated by the microlens array 302, penetrates the substrate 105 and is incident on the collimating grating array 101 of the optical chip 100, and is then 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 can be a unit, a one-dimensional linear array, or a two-dimensional planar 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 fibers to optical chips. This collimating grating is used together with a total reflection microprism and microlens array to collimate all light beams into parallel light for coupling, solving the problems of low efficiency and small alignment tolerance of conventional grating coupling or end-face coupling. The optical interface based on this enables pluggable and efficient coupling of the fiber array to the optical chip. By coupling light from the back of the optical chip, the optical device layout of the optical chip is not restricted by the position of the light output port or electrical interface when the optical chip is flipped and fanned out on the substrate. Instead, it can be freely arranged into a two-dimensional array, thereby improving the edge density of the optical fiber coupled to the optical chip and the integration of the optical chip.

[0045] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit the same. 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 solutions of the present invention with equivalents, and these modifications or equivalent replacements cannot cause the modified technical solutions to deviate from the spirit and scope of the technical solutions of the present invention.

Claims

1. An optical chip-fiber coupler based on a penetrating substrate collimating grating, characterized by: The optical chip includes a substrate on which a flip-chip optical chip is mounted. The optical chip includes at least one optical device, an optical waveguide array for input and output, and a collimating grating array. The collimating grating array is configured with a gradually varying period and duty cycle so that light output from the optical waveguide array is diffracted toward the substrate through the collimating grating array and propagates to the back of the optical chip as collimated light with a larger spot size, thereby providing a larger coupling tolerance. An optical coupling element array is disposed on the back of the optical chip at a position corresponding to the light output from the collimating grating array to couple the light to an optical fiber array. The optical chip and the optical fiber array are in a horizontal coupling relationship, and 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 optical coupling element array and the optical fiber array are connected to the substrate via a mechanical structure, wherein the mechanical structure includes an optical fiber connector arranged outside the optical fiber array and an optical interface seat on the substrate; The optical fiber connector is movably connected to the optical interface seat, and the large coupling tolerance of the collimating grating array enables the optical chip-fiber coupler to tolerate a large position error of the optical fiber array when the optical fiber connector is movably connected to the optical interface seat.

2. The optical chip-fiber coupler based on a trans-substrate collimating grating according to claim 1, characterized in that: 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 trans-substrate collimating grating according to claim 1, characterized in that: The substrate is made of Si, quartz, glass, ceramic or organic material, and a plurality of electrical chips are arranged on the substrate.

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

7. The optical chip-fiber coupler based on a trans-substrate collimating 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. 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, reflected by the metal high-reflection film, and then penetrating the collimating grating array interferes constructively with the light diffracted directly by the collimating grating array to the substrate.

8. The optical chip-fiber coupler based on a trans-substrate collimating grating according to claim 1, characterized in that: The material of the total reflection microprism is Si, quartz or glass. The reflective surface of the total reflection microprism is set at the hypotenuse and totally reflects 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 optical chip plane and aligning it with the optical fiber array. The two right-angled sides of the total reflection microprism are coated with an optical anti-reflection film, and the projected 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 trans-substrate collimating grating according to claim 2, characterized in that: The microlens array is mounted on the end face of the optical fiber array or is arranged on a total reflection microprism. 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 trans-substrate collimating 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.

Images