Detachable connection of an optical connector using a base having features for integral optical coupling and detachable mechanical coupling

Abstract

The present invention provides a removable connection of an optical connector using a base having features for integrated optical coupling and removable coupling. The base enables a removable passive alignment connection to the optical connector. The base is permanently attached and aligned to the PIC chip. The base includes an optical element that redirects and reshapes the incident light to follow the desired shape and path of the optical beam between the optical connector and the optoelectronic device. The base can include a combination of different optical elements having optical properties that produce the desired quality and direction of the optical beam. The base also includes passive alignment features corresponding to the passive alignment features of the opposing face of the optical connector. The base has a monolithic body provided with the optical element and the passive alignment features.

Description

Cross - reference to related applications

[0001] This application claims priority to (a) U.S. Provisional Patent Application No. 63 / 388,238, filed on July 11, 2022; (b) U.S. Provisional Patent Application No. 63 / 406,627, filed on September 14, 2022; (c) U.S. Provisional Patent Application No. 63 / 417,988, filed on October 20, 2022; and (d) U.S. Provisional Patent Application No. 63 / 512,011, filed on July 5, 2023. These applications are hereby incorporated by reference in their entirety as if their contents were fully set forth herein. All publications mentioned below are hereby incorporated by reference in their entirety as if their contents were fully set forth herein.

Technical Field

[0002] The present invention relates to a technique for coupling light to the input and output of optoelectronic components (e.g., photonic integrated circuits (PICs)), and more particularly, to the optical connection of optical fibers to PICs.

Background Art

[0003] A photonic integrated circuit (PIC) or an optical integrated circuit is part of an emerging technology that uses light rather than current as the basis of operation. PIC devices integrate multiple (at least two) photonic functions and are thus similar to electronic integrated circuits. The two main differences above are that photonic integrated circuits typically provide functions for information signals given at optical wavelengths in the visible spectrum or in the near - infrared range of 850 nm to 1650 nm.

[0004] PICs are used in a variety of applications in the fields of long-distance communication, measurement, and signal processing. PIC devices (in the form of photonic chip packages) typically use optical waveguides to implement and / or interconnect various on-chip elements, such as waveguides, optical switches, couplers, routers, splitters, multiplexers / demultiplexers, modulators, amplifiers, wavelength converters, optical-electrical (O / E) and electro-optical (E / O) signal converters (e.g., photodiodes, lasers), etc. The waveguides in PIC devices are usually on-chip solid light conductors that guide light by the refractive index contrast between the core and cladding of the waveguide.

[0005] One of the most expensive components in a photonic network is the optical fiber connector. For proper operation, a PIC typically needs to efficiently couple light between an external optical fiber and one or more on-chip waveguides. PIC devices are often required to have optical connections to other PIC devices, typically in the form of organized networks for optical communication. The connection distance can range from a few millimeters for inter-chip connections to several kilometers for long-distance applications at most. Since light can pass through the optical fiber at a very high data transfer rate (>25 Gbps) over long distances with low-loss optical fibers, optical fibers can provide an effective connection method. For proper operation, a PIC device needs to efficiently couple light between an external optical fiber and one or more on-chip waveguides. The advantage of using light as the basis for circuit operation in PIC devices is that the energy consumption for high-speed signal transmission is substantially lower than that of electronic chips. Therefore, an effective coupling between PIC devices and other optical devices such as optical fibers, which maintains this advantage, is an important aspect of PICs.

[0006] One approach to coupling an optical fiber to a PIC device (or PIC chip package) is to attach an optical fiber array to the edge of the PIC chip. Conventionally, the optical fiber array is aligned with elements on the PIC using an active alignment approach, in which the position and orientation of the optical fiber are mechanically adjusted until the amount of light transmitted between the fiber and the PIC is maximized. This is a time-consuming process that is typically done after the PIC has been diced from the wafer and implemented in a package. As a result, the connection of the optical fiber is left until the end of the manufacturing process. Once the connection is made, it is permanent and cannot be removed, separated, or detached, probably without breaking the integrity of the connection, in response to any desire to reattach the optical fiber array to the PIC. In other words, the optical fiber array cannot be removably attached to the PIC device, and fiber array connection and separation are destructive and non-reversible (i.e., not re-connectable).

[0007] The state of the art attempts to achieve tight alignment tolerances using polymer connector elements, but polymers have several fundamental disadvantages. First, polymers are flexible and deform easily under an externally applied load. Second, polymers do not have dimensional stability and can change size and shape when exposed to high temperatures, such as those found in computing and networking hardware. Third, the coefficient of thermal expansion (CTE) of polymers is much larger than that of the materials commonly used in PIC devices. Therefore, temperature cycling causes an alignment shift between the optical fiber and the optical elements on the PIC device. In some cases, the polymer cannot withstand the processing temperatures used when soldering the PIC device onto a printed circuit board.

[0008] Furthermore, it would be advantageous if an optical fiber connection could be made before dicing the individual PIC devices from the wafer; this is often referred to as wafer-level attachment. Manufacturers of integrated circuits and PICs often have expensive capital equipment capable of sub-micron alignment (e.g., wafer probers and handlers for testing integrated circuits), but companies that package chips typically have less capable machinery (typically several micron alignment tolerances not suitable for single-mode devices) and often use manual operations. However, it is not practical to permanently attach an optical fiber to a PIC before dicing, because the optical fibers would become entangled and interfere during the dicing operation and packaging procedure, and it is virtually impossible to manage the optical fibers when the PIC is pick-and-placed onto a printed circuit board and then soldered to the PCB at high temperature.

[0009] A further design challenge is to improve the optical and mechanical compatibility of the optical connector to the PIC device without elaborate or complex connector assemblies to implement a robust optical connection. Generally, PIC devices are packaged in a structure where the structural integrity can be compromised if the package is structurally modified to accommodate mechanical coupling of the optical connector. Furthermore, dicing of the PIC device from the wafer does not provide good reference for optical and physical alignment of the optical connector to the PIC device. Without modifying the PIC device, elaborate pedestals are often provided around the PIC device to facilitate mechanical and optical coupling by the optical connector. This increases the overall size of the structure. Additionally, PIC devices have different optical input / output configurations, which requires the optical connector to be designed to match the optical input / output configuration of the PIC device.

[0010] Patent Document 1 (assigned jointly to the assignees of the present application and incorporated herein by reference in its entirety) discloses a removable optical connector for optoelectronic devices. The disclosed removable optical connector includes the implementation of elastic averaging and provides an improved method for optically coupling the input / output of an optical fiber to a PIC, thereby improving cost, tolerance, manufacturability, usability, functionality, and reliability. As is known in the prior art, elastic averaging represents a subset of surface bonding types, where improved accuracy is derived from the averaging of errors across multiple contact surfaces. In contrast to kinematic design, elastic averaging is based on significantly overconstraining a solid with a number of relatively flexible members. When a preload is applied to the system, the elastic properties of the material average out the errors in the size and position of each contact feature with respect to the sum of the contact features across the solid. The reproducibility and accuracy obtained by elastic averaging may not be as high as those of a deterministic system, but the elastic averaging design allows for higher stiffness and lower local stress compared to kinematic bonding. In a well-designed and preloaded elastic averaging bond, the reproducibility is approximately inversely proportional to the square root of the number of contact points.

[0011] Most PIC devices require single-mode optical connections with stringent alignment tolerances, usually less than 1 micrometer, between the optical fiber and the PIC. Effective optical coupling to and from an on-chip single-mode waveguide to an external optical fiber is difficult due to the size mismatch between the single-mode waveguide and the light-guiding core in the optical fiber. For example, the dimensions of a typical silica optical fiber are approximately 40 times larger than those of a typical waveguide on a PIC. Due to this size mismatch, if the single-mode waveguide and the optical fiber are directly coupled, the modes of the waveguide and the optical fiber do not effectively couple, and unacceptable insertion losses (e.g., >20 dB) can occur.

[0012] Patent Document 2 (assigned jointly to the assignee of the present application and incorporated herein by reference in its entirety) discloses a removable edge coupler having a micromirror optical bench for a PIC, which provides a mechanism for bringing the mode sizes of the optical fibers and on-chip optical elements in an optical fiber array closer to each other and efficiently optically coupling the input / output of the optical fibers to a PIC device.

Prior Art Documents

Patent Documents

[0013]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0014] What is needed is an improved removable optical and mechanical coupling for connecting an optical connector to a PIC device that is low cost and improves flexibility, tolerance, manufacturability, usability, functionality, and reliability.

Means for Solving the Problems

[0015] The present invention overcomes the disadvantages of the prior art by providing a base in the form of an adapter for providing a bridge for removable / separable and re-connectable passive alignment coupling / connection that achieves high alignment accuracy. An optical connector (e.g., one that supports or is part of an optical bench that supports an optical fiber) is configured and structured to be removably attached in a non-destructive manner so as to be reconnected in an aligned state with the base. The base may be an integral part of an optoelectronic device (e.g., part of a photonic integrated circuit (PIC) chip), or it may be a separate component attached to or associated with the optoelectronic device and / or in an optical alignment reference.

[0016] The present invention will be described in relation to the illustrated embodiments. The base can be aligned to electro-optic elements (e.g., grating couplers, waveguides, etc.) within the optoelectronic device. The base is permanently aligned with respect to the optoelectronic device to provide an alignment reference for an external optical connector. The optical connector can be removably attached to the base via a "separable" or "removable" or "detachable" operation that precisely optically aligns the optical components / optical elements within the optical connector along a desired optical path to the optoelectronic device. In order to maintain optical alignment for each of connection and disconnection and reconnection, this connector needs to be precisely and accurately aligned with respect to the base. According to the present invention, the connector and the base are aligned with each other using passive mechanical alignment (e.g., kinematic, quasi-kinematic, and elastic averaging alignment) composed of geometric features on two bodies. The present invention will be described more specifically in relation to mechanical alignment based on elastic averaging alignment. As an introduction to the above, the present invention can be summarized as follows.

[0017] In one aspect of the present invention, the base includes one or more optical elements, which can reflect light by total internal reflection (TIR) of an opaque free surface exposed to the outside (e.g., air or refractive index matching material), reflect incident light directed from the outside to the free surface (i.e., the incident light is not directed through the body of the base), a reflective surface, or any other optical features and elements that can effectively redirect (i.e., reflect, bend, redirect, change the path, reshape (e.g., focus, collimate, diverge, converge, or branch)) the incident light from an optical connector and / or an optoelectronic device. The optical elements of the base redirect and / or reshape the incident light to follow a desired optical beam path between the optical connector and the optoelectronic device (i.e., align the optical axis of the optical connector with the optical axis of the optoelectronic device). The base may include a combination of different optical elements having optical properties that generate a desired optical beam quality and direction. Further, the base includes passive alignment features such as kinematic, quasi-kinematic, and elastic flat alignment features, which mate / complement with the passive alignment features on the opposite side of the optical connector. In one embodiment, the base comprises an integral monolithic body with the optical elements and passive alignment features. In another embodiment, the base can include separate bodies each having passive alignment features and optical elements separately.

[0018] In one embodiment, the base is a longitudinal glass substrate or plate having passive alignment features integrally formed on the upper surface of the base body (i.e., the surface facing the optical connector attached to the base). In a further embodiment, the base further includes passive alignment features integrally formed on the bottom surface of the base body facing the optoelectronic device. The passive alignment features are grouped into two sets, each set being located near opposite ends of the surface of the longitudinal plate. An array of optical elements (e.g., microlenses) is integrally formed on the base between the passive alignment features (i.e., not discrete lenses disposed on the surface). The passive alignment features and the array of optical elements are integrally defined on the base body in a geometric shape and relative position defined in a final forming step, and the alignment relationship of the passive alignment features with respect to the array of optical elements can be accurately defined. For example, in the case of a glass base body, the passive alignment features and the array of optical elements can be molded to define the final geometric shape and position of the array of optical elements and the passive alignment features.

[0019] If the base does not have passive alignment features on its bottom surface, the base can be optically aligned with and fixedly attached to the support surface (e.g., the top surface of a PIC device, or a grating coupler and / or waveguide on a support on a submount on a circuit board that optically communicates with the PIC device). The base may be visually aligned with the support surface using visual references defined on the support surface, and additionally or alternatively, may be optically aligned by determining an optical signal from a loopback optical channel on the support surface corresponding to a desired position of the base relative to the support surface. Once the base is optically aligned with the support surface, the base is fixedly attached to the support surface (e.g., by epoxy or solder). Thereby, the base provides a removable connection for an optical connector by means of mating passive alignment features on the support surface on its opposing mounting surface. If the base further has passive alignment features on its bottom surface and the support surface has mating passive alignment features, the base can be passively aligned and firmly attached to the support surface.

[0020] In another embodiment, the optical connector can first be coupled to the base. The optical connector is actively aligned with respect to the optoelectronic device (e.g., a PIC chip or an optical I / O chip) by positioning the base with respect to the optoelectronic device to obtain an optimal optical signal between the optoelectronic device and the optical connector (e.g., an optical fiber supported by the optical connector). The position of the base is fixed with respect to the optoelectronic device at the aligned position (e.g., using solder to hold the position of the base on a support for the optoelectronic device such as an interposer, a printed circuit board, a submount, etc.). The optical connector is then removed from the base, and the base can be permanently attached to the support (e.g., reflowing the solder) without changing its position on the support. Thereafter, the optical connector can be non-destructively repeatedly connected and disconnected and reconnected to the base without losing the original optical alignment obtained by the active alignment between the optical connector and the optoelectronic device. The optical alignment according to the original active alignment is maintained for each connection and disconnection and reconnection, precisely and accurately aligning the optical connector to the base.

[0021] In one embodiment, the base includes an integrated monolithic body with optical elements and passive alignment features. In another embodiment, the base can include separate bodies each having passive alignment features and optical elements separately.

[0022] In another embodiment, the base may be in the form of a silicon insert having an optically transparent body. The silicon insert may be integrally defined (e.g., by etching) with an array of passive alignment features and optical elements, facilitating direct connection on top of a PIC device or a grating coupler on a support surface. If a window is provided on a cooling plate above the PIC device, this window can be used to design the optical connector body, provide a rough alignment to guide the connection body, and achieve a removable connection based on the passive alignment features.

[0023] In another aspect of the present invention, the base can be configured to removably edge couple an optical connector to a waveguide that terminates at an end of an optoelectronic device. The base may be configured using different optical elements to define a desired beam path having a desired beam shape to maximize the optical coupling of optical signals entering and exiting the optoelectronic device and optical signals entering and exiting the optical connector. For example, the optical beam can first be expanded between the optical connector and the optoelectronic device and ultimately focused onto waveguides on the optoelectronic device and the optical connector. The transmission of the expanded beam requires lower tolerances, and the high tolerances are maintained in terms of focusing the beam onto the target device.

[0024] In a further embodiment, the base is in the form of an interposer for guiding light to / from an exit end of an array of waveguides on an upper or lower surface of an optoelectronic device (e.g., SiPIC). The interposer includes an array of optical elements for guiding light from the optical connector and prongs that extend outwardly across the surface of the optoelectronic device on both sides of the array of optical elements. The prongs are integrally formed with passive alignment features for passive alignment with passive alignment features defined on the surface of the optoelectronic device, thereby optically aligning the array of optical elements with the array of waveguides.

[0025] In a further embodiment, the base in each of the above-described embodiments may be an integral part of the optoelectronic device or a support for the optoelectronic device.

[0026] As an introduction to the above content, the present invention will be further discussed below to support the features recited in the claims.

[0027] In addition to the preferred usage modes, for a more complete understanding of the nature and advantages of the present invention, please refer to the following detailed description read in conjunction with the accompanying drawings. In the following drawings, throughout the drawings, like reference numerals refer to the same or similar parts.

Brief Description of the Drawings

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DETAILED DESCRIPTION OF THE INVENTION

[0029] Hereinafter, the present invention will be described with reference to the drawings and various embodiments. The present invention is described with respect to the best mode for achieving the object of the present invention, but those skilled in the art will understand that a plurality of variations can be realized in consideration of these teachings without departing from the spirit and scope of the present invention.

[0030] The present invention overcomes the drawbacks of the prior art by providing a pedestal in the form of an adapter for providing a bridge for removable / separable and reconnectable passive alignment coupling / connection that achieves high alignment accuracy. An optical connector (e.g., supporting or being part of an optical bench that supports an optical fiber) is configured and structured to be removably attached in a non-destructive manner for reconnection in an aligned state with the pedestal.

[0031] The pedestal may be an integral part of an optoelectronic device (e.g., part of a photonic integrated circuit (PIC) chip), or a separate component attached to, associated with, and / or optically aligned with respect to the optoelectronic device. The concept of passive alignment coupling of the present invention will be discussed below with reference to an example of an optical connector that optically couples a PIC device as an optoelectronic device to the input / output ends of optical components (e.g., optical fibers) provided in and supported within an optical bench. The present invention is applicable for providing removable / reconnectable forms of structures and components used in other fields.

[0032] FIG. 1A shows a pedestal 100 acting as an adapter, or an interposer, or an insert having passive alignment features defined on its upper surface, according to a simple embodiment of the present invention for illustrating the concept of the present invention.

[0033] In one aspect of the present invention, the pedestal 100 includes one or more optical elements. In the illustrated embodiment, the optical element is in the form of a microlens array L. In further embodiments discussed below (e.g., see FIGS. 9A - 9D and 11A - 11F), additional and / or different optical elements are formed on the pedestal and reshape and reflect incident light by total internal reflection (TIR) of an opaque free surface exposed to the outside (e.g., air or refractive index matching material), and reflect incident light directed from the outside towards the free surface (i.e., the incident light is not directed through the body of the pedestal). The optical elements of the pedestal 100 redirect and / or reshape the incident light to follow a desired optical beam path between the optical connector and the PIC chip P (i.e., to align the optical axis of the optical connector 10 with the optical axis of the PIC chip P).

[0034] Furthermore, the base 100 includes passive alignment features E2 such as kinematic, quasi-kinematic, and elastic averaging alignment features, which are adapted / complemented with the passive alignment features E1 on the opposing surface of the optical connector 10. In the illustrated embodiment, the passive alignment features are based on surface features for elastic averaging connection. U.S. Patent Application Publication No. 2016 / 0161686 and U.S. Patent No. 11,500,166 disclose elastic averaging features suitable for connecting an optical connector to a support base.

[0035] In the illustrated embodiment, the base 100 includes an integral monolithic body B2 having a microlens array L and passive alignment features E2.

[0036] In the illustrated embodiment, the base body B2 is a longitudinal glass substrate or plate having passive alignment features E2 integrally formed on the upper surface of the base body B2 (i.e., the surface facing the optical connector 10 when attached to the base). The passive alignment features E2 are grouped into two sets, each set being near the opposing ends of the surface of the longitudinal plate. A microlens array L is integrally formed on the base 10 between the passive alignment features (i.e., not as separate lens elements disposed on the surface). The arrays of passive alignment features E2 and microlens array L may be integrally defined on the base body B2, with their geometric shapes and relative positions defined in a final forming step, thereby accurately defining the alignment relationship of the passive alignment features E2 with respect to the microlens array L. For example, in the illustrated embodiment of a glass base body B2, the passive alignment features E2 and microlens array L can be formed so as to define the final geometric shapes and positions of the microlens array L and passive alignment features E2. The alignment features E2 and microlens array L manufactured on the same substrate using a single tool / mask minimize the positional error between these two features.

[0037] Glass is a good material for the base 100, and the coefficient of thermal expansion (CTE) can be matched to that of the silicon of the PIC chip P (CTE about 3×10 -6 K -1 ). Glass forming enables an optical design and a mechanical design optimized for operation at -100°C. The glass can withstand solder reflow at temperatures up to 280°C.

[0038] Figures 2A and 2B schematically show the glass forming process disclosed in the publication by Zhou et al. ["A review of the techniques for the mold manufacturing of micro / nanostructures for precision glass molding". Intl. Jrnl of Extreme Manufacturing. 3 (2021). 042002], which can be adapted to form the base 100 according to an embodiment of the present invention. Figure 2A is a schematic diagram of a PFLF7-60A molding machine. Figure 2B is a diagram showing the stages of a glass forming process using such a molding machine, related to the forming temperature and forming pressure at various stages of the forming process.

[0039] Figures 3A and 3B show optically aligning a glass pedestal to a PIC device according to one embodiment of the present invention. In the illustrated embodiment, the pedestal 100 is optically aligned with a support surface (e.g., the upper surface of the PIC chip P, or a grating coupler and / or waveguide on a support on a submount on a circuit board that optically communicates with the PIC chip P) and can be fixedly attached to the support surface. In FIG. 3A, the pedestal 100 may be visually aligned with the support surface using visual references defined on the support surface. In FIG. 3B, when the pedestal 100 is optically aligned with the support surface, the pedestal 100 is fixedly coupled to the support surface (e.g., by epoxy or solder). The entire package can undergo solder reflow and other packaging processes. The bottom surface of the pedestal body B2 may be plated to enable solder reflow attachment to the PIC chip P.

[0040] Figures 3C and 3E illustrate an alternative or additional optical alignment process of the base 100 by determining an optical signal from a loopback optical channel on a support surface corresponding to a desired position of the base with respect to the support surface. Referring to Figure 3C, a gripper GR having a mechanical passive alignment feature similar to the passive alignment feature E1 on the optical connector 10 is used to pick and place the base 100 onto the PIC chip P. The base 10 is first aligned to the PIC chip P using a visual fiducial VF provided on the PIC chip during packaging. Thereby, an alignment accuracy of several micrometers can be achieved. This enables "first light" for more accurate optical alignment. Next, the gripper GR is aligned more precisely using optical alignment. The gripper GR can incorporate a laser light source LS and a photodiode PD. Light is injected into the "loopback" LB (input port IP, waveguide WG, output port OP) on the PIC chip P. During this optical alignment process, the functional waveguides of the channels Ch1 to ChN of the PIC chip P are not used. This optical alignment process can refer to the optical passive alignment of an optoelectronic device of an optical connector assembly in the process disclosed in U.S. Patent No. 9,897,769, which was assigned jointly to the assignee of the present application.

[0041] Figures 4A - 4C show a removable connection of an optical connector to a glass base 100 joined to a support surface, according to an embodiment of the present invention. As shown in Figure 4A, the optical connector 10 includes an array of micromirrors M corresponding to an array of microlenses L on the base 100. The optical connector 10 also accurately supports the exit ends of the optical fibers OF with respect to the micromirror array M and thus also with respect to the passive alignment feature E1. In the illustrated embodiment, the optical connector 10 comprises a body B1 that supports an array of optical fibers OF that transmit optical signals. Thus, the base 100 comprises a body B2 that provides an alignment reference for an external optoelectronic device (e.g., a PIC chip P or an I / O PIC chip for an ASIC chip (e.g., a CPU, GPU, switch ASIC)) that communicates with the optical fibers OF within the optical connector 10 and optical signals.

[0042] More specifically, the body B1 of the connector 10 defines a base for supporting the optical fiber array OF, and this base has a plane defined by a two-dimensional planar array of alignment features E1 integrally defined on the surface of the base of the body B1. In this embodiment, the connector 10 incorporates a micro-optical bench OB for supporting and aligning the optical fiber array FA. The optical fiber array has a plurality of optical fibers OF protected by a protective buffer and a matrix / jacket layer P. The base of the body B1 of the connector 10 includes an alignment structure with an open groove G for holding the bare section of the optical fiber OF (having a cladding exposed without the protective buffer and matrix / jacket layer J), and defines a structured feature including a structured reflective surface (e.g., eight mirrors M). The open groove G is sized to receive the end of the optical fiber OF in an aligned state with respect to the first array of mirrors M along the optical path, and is arranged to be accurately positioned. The end face (input / output end) of each optical fiber OF is held at a predetermined distance from the corresponding mirror M. In the illustrated embodiment, a transparent glass, quartz, or sapphire plate cover covers the exposed surface on the optical bench OB to protect the mirror M. In one embodiment, the connector 10 may be filled with a refractive index matching epoxy between the mirror surface M and the plate cover.

[0043] The base 100 provides a removable connection for the optical connector 10 and adapts the passive alignment features E1 on its opposing mounting surface with respect to the support surface for the PIC chip P. FIG. 4B shows attaching the optical connector 10 with the mating matching passive alignment features E1 to the passive alignment features E2 on the base 100. FIG. 4C shows the situation after attaching the mating passive alignment features E2 of the optical connector 10 to the passive alignment features E2 on the base 100, where the optical path entering and exiting the micro-mirror array M passes through the corresponding micro-lens array L. The passive alignment features E1 and E2 provide accurate optical alignment, reproducibility, and removability for this optical path.

[0044] Figure 1B shows a base F' having an additional passive alignment feature E2' for passive alignment to a PIC chip P, according to another embodiment of the present invention. In the illustrated embodiment, the base 100' further includes a passive alignment feature E2' integrally formed on the bottom surface of the base body B2' facing the PIC chip P. The additional alignment feature E2' on the bottom surface of the base body B2' enables the base body B2' to be passively aligned to the surface of the PIC chip P when receiving portions and complementary features are present on the surface of the PIC chip P. The passive alignment feature E2' may be similar to the feature E2 on the upper surface of the main body base B2'.

[0045] Figure 5 shows the passive alignment of a glass base 100" to a PIC chip P, according to another embodiment of the present invention. In the illustrated embodiment, the base 100" has additional passive alignment features E2" on its bottom surface, and the support surface of the PIC chip P has corresponding passive alignment features E". Using these, the base 100" can be passively aligned to the PIC chip P. Specifically, in this embodiment, the precision alignment feature E2" includes three hemispheres on the bottom surface of the base body B2", which have good positional tolerances with respect to the microlens array L. Complementary precision alignment features including three V-grooves are provided on the upper surface of the PIC chip P in alignment with the grating coupler within the PIC chip P. A reference mark VF" may be provided on the upper surface of the glass body B2", and this is used to visually align the base 100" to a complementary reference mark (if provided; not shown) on the PIC chip P to provide a first light. The base 100" can be passively aligned and fixedly attached to the support surface of the PIC chip P.

[0046] In another embodiment, the base 100 can include separate bodies each having passive alignment features and optical elements. FIG. 6 shows a glass base 101 with one or more separate and unconnected components according to another embodiment of the present invention. In this embodiment, the alignment base 101A and the microlens array insert L1 are separate components, and the alignment base 101A can be on the upper surface of the PIC chip P or outside the PIC chip P. This configuration is less expensive because it minimizes the area of the functional elements and reduces the cost of glass molding. However, the number of parts per molding operation is greater.

[0047] According to the above-described embodiments, the base 100 (and its variants) can be aligned to electro-optic elements (e.g., grating couplers, waveguides, etc.) inside or outside the optoelectronic device (see also further explanations related to FIGS. 4, 5, 9, and 11). The base 100 is permanently positioned with respect to the optoelectronic device (e.g., PIC chip P) to provide an alignment reference for the external optical connector 10. The optical connector 10 can be removably / attachably mounted to the base F via a "separable" or "removable" or "detachable" operation that accurately optically aligns the optical connector 10 with the optoelectronic device along a desired optical path. To maintain optical alignment for each connection and disconnection and reconnection, this connector needs to be accurately and precisely aligned with respect to the base. According to the present invention, the optical connector and the base are aligned with each other using passive mechanical alignment (e.g., kinematic, quasi-kinematic, and elastic averaging alignment) constructed from geometric features on two bodies. In certain embodiments, the present invention more specifically employs mechanical alignment based on elastic averaging alignment.

[0048] In one embodiment, each mirror M has an exposed reflective-free side facing away from the body B1, which is the exposed free surface of the base of the body B1 (i.e., the surface exposed to air or a surface that is not inside the body of the base of the optical bench). The exposed reflective-free side includes a structured reflective surface profile that is oriented such that light enters and exits the optical fiber OF and the base 100 (including alternative embodiments disclosed herein). Each mirror M bends, reflects, and / or reshapes the incident light. Depending on the configuration and shape (e.g., curvature) of the structured reflective surface profile, the mirror M can collimate, expand, or focus the incident light beam. For example, the structured reflective surface profile can include one of the following geometric shapes / profiles: (a) an ellipsoid, (b) an off-axis parabola, or (c) other freeform optical surfaces. For example, the mirror surface may have any of the following surface geometric curvature functions, individually or in combination, to provide optical power: ellipsoidal or hyperbolic conical foci, toroidal aspheres with various numbers of even or odd aspherical terms, X-Y aspheric curves with various numbers of even or odd terms, Zernike polynomials of various orders, and various families of simpler surfaces included in these functions. The surface may also be a freeform surface without symmetry along any plane or vector. The mirror M can be defined on the body B1 by stamping a malleable metal material. Various malleable metals that can be stamped with tool steel or tungsten carbide tools can form the body of the mirror and include any 300 or 400 series stainless steel, any composition of kovar, any precipitation or solution-hardened metal, and any alloy of Ag, Al, Au, Cu. At wavelengths above 1310 nm, aluminum has a high reflectivity (>98%) and can be economically formed by stamping. The reflective surface of the metal portion that makes up the mirror can be any of the above metals or any highly reflective metal coating applied by sputtering, evaporation, or plating processes.

[0049] Figures 7A - 7F illustrate embodiments of the present invention that also provide extended beam optical coupling. Figure 7A shows the connection of an optical fiber OF to a photonic integrated circuit (PIC) P1 via an optical connector OC. The PIC shown in Figure 7E has a 2D array of optical I / O ports through which light enters and exits the PIC. The pedestal GF shown in Figure 7D includes passive alignment features and a 2D lens array. The pedestal GF can be fabricated from silicon or glass. The silicon lens insert SI shown in Figures 7B and 7C is also attached to the end face of the optical connector OC. This connection follows another embodiment of the present invention. The passive alignment features on both the silicon lens insert SI and the pedestal GF ensure that the lens arrays on SI and GF are aligned with high coupling efficiency. The lens arrays within the silicon insert SI and the pedestal GF provide an extended beam interface. The silicon insert SI is integrally defined (e.g., by etching) with the passive alignment features and an array of optical elements, facilitating direct connection to the top of a PIC device or grating coupler on a support surface.

[0050] In FIG. 7B, the male side of the silicon front insert SI has a 2×22 channel microlens ML, which are positionally aligned with the alignment features AF (protrusions) on the silicon insert SI, as shown in FIG. 7B. In FIG. 7C, the silicon insert SI has stop holes H (e.g., 125.5 μm in diameter) from the back side of the 2×22 channel array, which are aligned with the microlens array ML shown in FIG. 7B. These stop holes receive the tip of the optical fiber and passively align the silicon insert SI with the array of optical fibers in the optical connector OC. The side shown in FIG. 7C faces the end of the optical fiber in the optical connector OC. With respect to the glass base GF, FIG. 7D shows a parallel array of alignment features AG that match the 2×22 array of microlenses LA and the female alignment features AC on top of the PIC chip P1 shown in FIG. 7F. FIG. 7E shows alignment features AG' that complement the alignment features AF on the male side of the silicon insert SI shown in FIG. 7B. The PIC chip P1 shown in FIG. 7F. FIG. 7F also shows a 2×22 array of microlenses on top of the PIC chip P1.

[0051] FIG. 7G shows an implementation form of the silicon lens insert SI in the optical connector OC for direct coupling to the PIC chip P1 without using the glass microlens array shown in FIGS. 7D and 7E. In the embodiment of FIG. 7G, the output of the microlens array ML on the silicon insert is expanded within the PIC, which establishes a path for a higher number of fibers (e.g., 3 or 4 rows).

[0052] FIGS. 8A and 8B show alternative uses of the optical connector in the bundled optical components. When a window W is provided on the thermal diffusion cooling plate CP above the PIC device, the optical connector body is designed to use this window to provide a rough alignment for guiding the connector body and achieve an accurate removable connection based on passive alignment features.

[0053] In another aspect of the present invention, the base can be configured to removably edge-couple an optical connector to a waveguide that terminates at an end of an optoelectronic device. The base may be configured using different optical elements to define a desired beam path having a desired beam shape, maximizing the optical coupling of optical signals to / from the optoelectronic device and to / from the optical connector. For example, the optical beam can first be expanded between the optical connector and the optoelectronic device and ultimately focused onto waveguides on the optoelectronic device and the optical connector. Transmission of the expanded beam requires lower tolerances, and high tolerances are maintained in focusing the beam onto the target device.

[0054] Figures 9A and 9D show the mounting configuration of the base F1 as an edge coupler to the PIC chip C according to another embodiment of the present invention. In this embodiment, the optical connector OP has an alignment cover plate CV1 formed with passive alignment features PA1 facing the base F1. The cover plate CV1 is provided with through holes for light to pass along the optical path LP1. In this embodiment and the embodiment of FIGS. 12A - 12F, the base F1 acts as a glass bridge for directing and reshaping the optical path LP1. Similar to the previous embodiment, the upper surface of the base F1 is formed with passive alignment features PA2. The base F1 may be supported on the support structure SS and on top of the PIC chip C, and the support structure SS is spaced from the edge of the PIC chip C by only the space SP, thus forming a glass bridge structure. In particular, the base F1 includes an array of protrusions or a single connection protrusion PT1 on the lower side facing the PIC chip C, providing an array of reflective surfaces by total internal reflection (TIR) corresponding to the number of optical fibers OF, the number of mirror arrays M1, and the channels in the PIC chip to be coupled. As clearly shown by the enlarged view of FIG. 9C, the protrusion PT1 is received within the space SP, and the protrusion PT1 is located below the upper surface of the PIC chip C, enabling it to direct light to the waveguide or other optical elements or components on the upper surface of the PIC chip C. An array of glass waveguides may be provided at the bottom of the base F1 to guide light to and from the mirror at the protrusion PT1. Similar to the previous embodiment, the detachable coupling between the optical connector OP and the PIC chip is achieved by the passive alignment of the features PA1 and PA1 between the cover plate CV1 and the base F1 as shown in FIG. 9D. Referring again to FIG. 9A, the optical path LP1 is an extended parallel beam between the mirrors M1 and M2 and is focused onto the end of the optical fiber OF and the waveguide FWG. Both the mirror surfaces M1 and M2 are aspherical mirrors.

[0055] Figures 10A and 10B illustrate a perspective view of the base F1 according to an embodiment of the present invention; Figures 10C and 10D illustrate different optical elements (e.g., lenses, reflective surfaces) and / or different reflection geometries deployed on the base. In Figure 10C, the reflective surface at the protrusion PT1 is an aspherical mirror that refracts and collimates the incident light between M1 and M2 (or vice versa depending on the direction of light propagation). This is the same as the embodiment shown in Figure 9C. In Figure 10D, the mirror M2' is a plane within the protrusion PT1' of the base F1', and does not collimate the incident light. Instead, an aspherical lens AL is provided on the upper surface of the base F1' corresponding to the position of the through opening TO in the cover plate CV1, which functions to collimate the light beam between the mirror M2' and M1. Various optical elements (e.g., lenses) and / or reflection geometries may be used to obtain the desired light beam shape and direction. Further examples are shown in Figures 11A - 11F, which illustrate various bases employing different optical elements for optical coupling to a PIC device according to alternative embodiments of the present invention. Some of the components similar to those in the embodiment of Figure 9 will not be described below. The differences are emphasized below.

[0056] In the embodiment of Figure 11A, a pocket is defined in the upper part of the base F2, which receives an optical isolator that prevents optical power from being reflected along the optical interconnection back to the laser source and damaging the laser. The optical isolator functions as a one - way valve that allows light to propagate in only one direction.

[0057] The embodiment of Figure 11B corresponds to the embodiment of Figure 10D. Since the surface of the mirror M2' is a flat reflective surface within the base F1', an aspherical lens is applied to collimate the light.

[0058] In the embodiment of FIG. 11C, the mirror M2 in the base F3 is the same as the aspherical mirror M2 in the embodiment of FIG. 9, but the mirror M1' in the optical connector OP3 is a plane mirror. Therefore, the re-focusing lens RL is applied to the upper part of the base F3 at a position corresponding to the through-opening TO of the cover plate CV1 to collect the light passing through the base F3 (or collimate the light entering the base F3 according to the traveling direction of the light).

[0059] In the embodiment of FIG. 11D, the base F1 is the same as the base F1 in FIGS. 9 and 10D. However, in this embodiment, an aspherical lens is provided below the cover plate CV4 (corresponding to the position of the through-hole TO in the previous embodiment) to collect / collimate the light along the optical path between the mirrors M1' and M2. The mirror M1' is a plane mirror, and M2 is an aspherical mirror as in the previous embodiment. In this embodiment, the cover plate CV4 does not have a through-opening TO for the light beam to pass through.

[0060] In the embodiment of FIG. 11E, the base F5 has a through-opening FTO that defines an exposed aspherical reflecting mirror surface M5. The mirror M1 in the optical connector OP is an aspherical mirror. The mirror M5 may be metal-coated to improve the reflectivity.

[0061] In the embodiment of FIG. 11F, a cavity CAV for receiving the protrusion PT6 of the base F6 is provided on the upper surface of the PIC chip C'. In this embodiment, the reflecting surface in the protrusion PT6 is a flat reflecting surface M2'. Therefore, similar to the case of the embodiment of FIG. 11B, an aspherical lens is provided on the upper part of the base F6 at a position corresponding to the through-opening TO in the cover CV1.

[0062] In all of the above-described embodiments of the base having a protrusion on the bottom surface, it should be noted that the protrusion is a longitudinal structure as shown in FIGS. 10A and 10B. In the embodiment of FIG. 11F, the cavity CAV is a longitudinal groove on the upper surface of the PIC chip C' for accommodating the longitudinal protrusion at the bottom of the base F6.

[0063] In a further embodiment, the pedestal FF is in the form of an interposer for guiding light to / from the exit ends of an array of waveguides on the top or bottom surface of an optoelectronic device (e.g., PIC chip C). FIGS. 12A - 12F show the mounting configuration of the pedestal as an edge coupler to a PIC chip having waveguides on its top surface according to another embodiment of the present invention. In this embodiment, the pedestal FF includes an array of exposed micromirrors MM defined on the body FB' corresponding to the number of exit ends of the waveguides CWG on the top surface of the PIC chip CC for guiding light from an optical connector (not shown). The pedestal FF includes protrusions PP extending outwardly from the body FB across the surface of the PIC chip CC on both sides of the array of micromirrors MM. The protrusions PP are integrally formed with passive alignment features PAF1 for passive alignment with passive alignment features PAF2 (e.g., etched) defined on the surface of the PIC chip CC, thereby optically aligning the mirror array MM with the waveguide array CWG. In the illustrated embodiment, the passive alignment feature PAF1 is a hemispherical protrusion that conforms to the rectangular opening and tapered bottom of the passive alignment feature PAF2 on the PIC chip CC.

[0064] FIGS. 13A - 13D show the mounting configuration of the pedestal FF' as an edge coupler to a PIC chip CC' having waveguides CWG' on its bottom surface according to another embodiment of the present invention. The pedestal FF' is similarly constructed with protrusions PP' extending from the body FB' and has similar passive alignment features PAF1' that match similar passive alignment features PAF2'. However, in contrast to the previous embodiment of FIG. 12 where the micromirror MM is oriented opposite to the extending direction of the hemispherical passive alignment feature PAF1, when the waveguide CWG' is on the bottom surface of the micromirror MM', the micromirror MM' is oriented in the same direction away from the passive alignment feature PAF1' on the upper side of the protrusion PP'.

[0065] Instead of using glass for the base described in the above embodiments, a silicon material can be alternatively used, which is optically transparent to infrared light and can be manufactured with better dimensional tolerances than 100 nanometers, so that similar advantages can be obtained.

[0066] Note that FIGS. 12E and 13C are not side views or cross-sectional views taken only of the waveguide CWG / CWG' or the mirror MM / MM'.

[0067] According to the present invention, the optical connector and the base define a removable coupling with an optical element formed on the base and provide reshaping and / or redirection of light. Further, the removable elastic average coupling between the optical connector and the base is defined without using any complementary alignment pins and alignment holes.

[0068] As described above, the present invention has been specifically shown and described with reference to the preferred embodiments. However, those skilled in the art will understand that various changes can be made in terms of form and details without departing from the spirit, scope, and teachings of the present invention. Therefore, the invention disclosed herein should be regarded as for illustrative purposes only, and the scope should be limited only as defined in the appended claims.

Claims

1. A removable connection for optical connectors and optical connection points, A base provided along the optical path between the optical connector and the optical connection point, supporting the optical connector in an optically aligned manner with the optical connection point, and facilitating the removable connection of the optical connector to the base; and A passive alignment feature on the surface of the base to provide a removable connection of the optical connector to a suitable passive alignment feature Equipped with, The base includes at least one optical element that reshapes and / or redirects incident light between the optical connector and the optical connection point. The position of the optical element is defined with respect to the passive alignment feature portion on the base to maintain optical alignment for the removable connection of the optical connector to the base. The base is attached to the optical connection point. A removable connection characterized by the following:

2. The removable connection according to claim 1, characterized in that the base allows incident light along the optical path to be transmitted from the upper surface to the lower surface or from the lower surface to the upper surface of the base.

3. The removable connection according to claim 2, characterized in that the optical element of the base comprises at least one of a lens and a reflective surface for reshaping and / or redirecting light between the optical connector and the optical connection point.

4. The removable connection according to claim 3, characterized in that the base may include a combination of different optical elements having optical properties that produce a desired light beam quality and direction.

5. The removable connection according to any one of claims 1 to 4, characterized in that the base comprises an integrated monolithic body having the optical element and the passive alignment feature portion.

6. The removable connection according to any one of claims 1 to 4, characterized in that the base comprises a separate body separately comprising the passive alignment feature portion and the optical element.

7. The removable connection according to claim 1, characterized in that the base is a glass substrate having a passive alignment feature integrally formed on the upper surface of the base body facing the optical connector attached to the base.

8. The removable connection according to claim 7, wherein the base further comprises a passive alignment feature portion integrally formed on the bottom surface of the base body, which is attached to the optical connection point.

9. The removable connection according to claim 7 or 8, characterized in that the passive alignment feature portions are grouped into two sets, each set located near opposing edges on the surface of the substrate, and an array of optical elements is integrally formed on the substrate between the passive alignment feature portions.

10. The removable connection according to claim 9, characterized in that the passive alignment feature portion and the array of optical elements may be integrally defined on the base body, and the geometric shape and relative position are defined in the final forming step so that the alignment relationship of the passive alignment feature portion with respect to the array of optical elements is accurately defined.

11. The removable connection according to claim 1, characterized in that the base includes an optically transparent glass or silicon insert and has an optically transparent body defined integrally with the passive alignment feature portion and the array of optical elements to facilitate direct connection to the optical connection point.

12. The removable connection according to claim 11, wherein the base is configured to be removable edge-coupled to a waveguide terminating at the end of an optoelectronic device, and the base includes at least one reflective surface.

13. The removable connection according to claim 11 or 12, characterized in that the base includes a reflective surface on a projection from the bottom of the base; the optical connector has an alignment cover plate formed with a passive alignment feature facing the passive alignment feature on the upper surface of the base, and the base acts as a glass bridge for directing and reshaping light between the optical connector and the end of the optoelectronic device.

14. The removable connector according to claim 11 or 12, wherein the base is in the form of an interposer for guiding light to and from the exit end of an array of waveguides on the top or bottom surface of an optoelectronic device (e.g., SiPIC), the interposer includes an array of optical elements for guiding light from an optical connector, and projections on both sides of the array of optical elements extending outward across the surface of the optoelectronic device, the projections being integrally formed with passive alignment features for passive alignment defined on the surface of the optoelectronic device, thereby optically aligning the array of optical elements with the array of waveguides.

15. The removable connection according to any one of claims 1 to 4, 7, 8, 11 and 12, characterized in that the optical connection point includes an optoelectronic device.

16. The removable connection according to any one of claims 1 to 4, 7, 8, 11 and 12, characterized in that the optoelectronic device includes a photonic integrated circuit (PIC) chip.

17. The removable connection according to any one of claims 1 to 4, 7, 8, 11 and 12, characterized in that the passive alignment feature is structured and configured to provide mechanical alignment based on one of kinematic alignment, quasi-kinematic alignment and elastic mean alignment.

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