Individually defined optical elements for use in an optical interconnect module with wirebonded components

Abstract

An individually aligned optical element is incorporated in an optical interconnect module to enable efficient optical communication between an electrooptic component and an optical waveguide. Electrical connections to the electrooptic component are made using wirebonds attached to wirebond pads on a first surface of the electrooptic component. The individually aligned optical element is defined relative to either an active area on the first surface of the electrooptic component or a core of an optical waveguide. The optical element may be situated within or on a surface of a transparent substrate, within or on a surface of an optical block, or directly within or on a surface of an encapsulant covering the electrooptic component. There may be a plurality of active areas and optical waveguides, and each active area and optical waveguide has a corresponding optical element which is individually aligned.

Description

INDIVIDUALLY DEFINED OPTICAL ELEMENTS FOR USE IN AN OPTICAL INTERCONNECT MODULE WITH WIREBONDED COMPONENTSCROSS-REFERENCE TO RELATED APPLICATIONS

[0001] The present application claims priority to US Prov. App. No. 63 / 638,175 filed on April 24, 2024, US Prov. App. No. 63 / 672,967 filed on July 18, 2024 and US Prov. App. No. 63 / 760,078 filed on February 18, 2025, all of which are incorporated herein by reference in their entireties.TECHNICAL FIELD

[0002] The present disclosure relates to an arrangement and method of establishing efficient optical coupling between an electrooptic component and an optical waveguide in an optical interconnect module.BACKGROUND

[0003] Optical communication channels, using modulated light signals, may be used to rapidly and reliably transmit information in a variety of applications such as fiber optic communication networks, server farms, or computer systems.

[0004] Optical fiber networks have advantages over other types of networks such as electrically conductive cable-based networks. Many existing electrically conductive cable networks operate at near maximum possible data transmission rates and at near maximum possible distances for copper wire cable technology. Fiber optic networks may be used to reliably transmit data at higher data rates over further distances than is possible with copper cable networks.

[0005] Computer systems employing high speed optical interconnect modules may provide improved performance when compared to other computer systems. The performance of some computer systems can be restricted by the rate that computer processors can access memory orcommunicate with other components in the computer system. The restriction can be due, in part, to the physical limitations of data interconnects such as electrical connections. For example, electrical pins with a particular size and / or surface area that may be used in electrical connections may only be capable of transmitting a specific data transfer rate, and in turn this may limit the maximum bandwidth for data signals. In some circumstances, such connections may result in bottlenecks when the maximum bandwidth of connections becomes a performance limiting factor. High speed optical interconnect modules using light signals may permit transmission of information at increased data rates to decrease or eliminate such bottlenecks.

[0006] Although modulated light signals may be used to transmit data at increased data rates in fiber optic networks, computer systems or other applications, almost all memory, switching, and processing components of such systems use electrical signals. Accordingly, optical interconnect modules, which connect various elements within the network may incorporate electrooptic assemblies that convert electrical signals to optical signals, convert optical signals to electrical signals, or convert both electrical signals to optical signals and optical signals to electrical signals. A component of an electrooptic assembly is an optical engine, which includes an electrooptic (E / O) component, such as a laser, photodetector, or photonic integrated circuit, that provides optical-to- electrical and / or electrical-to-optical conversion in high-speed communication systems. The optical interconnect module may further include a microcontroller that controls operation of the optical engine. Preferably the optical interconnect module is easily integrated into a computer or communication system from an electrical, mechanical and thermal standpoint. Examples of optical interconnect modules include packages compliant with multi-source agreement standards such as QSFP, QSFP-DD, OSFP, COBO, and many others. Optical interconnect modules may be mounted on a front panel of an electronics rack, adjacent a processing element mid-board on a host circuit board, or co-packaged with a processing element on a processing element package substrate.

[0007] The optical interconnect module may be a transmitter, a receiver, or a transceiver. In a transmitter, the optical interconnect module converts electrical signals received from an electrical component into optical signals. In a receiver, the optical interconnect module converts received optical signals into electrical signals that are transmitted to an electrical component. In atransceiver, the optical interconnect module both converts electrical signals into optical signals and converts optical signals into electrical signals.

[0008] Components typically included in the optical interconnect module, such as E / O components, like a laser, photodetector, and photonic integrated circuit, and associated electrical elements like a laser driver and transimpedance amplifier (TIA) may be available with either wirebond pads configured to make a wirebond electrical connection to an adjacent electrical element or with flip-chip pads configured to make a flip-chip electrical connection to an underlying substrate. It is generally easier to maintain good signal integrity at high rates with a flip-chip electrical connection as compared to a wirebond connection, since the path length between the connected electrical pads is shorter. In some cases, component availability or component cost may dictate which type of electrical connection is used in the optical interconnect module. In the wirebond arrangement, the laser / photodetector is generally mounted on a substrate such that the wirebond pads and optically active area of the laser / photodetector face away from an underlying substrate. In the flip-chip arrangement, the laser / photodetector is generally mounted on a substrate such that the flip-chip pads and optically active area of the laser / photodetector face towards an underlying substrate. The architecture of an optical interconnect module using wirebondable components is thus typically different from a module using flip-chip components. The present application describes an optical interconnect module that uses at least some wirebonded components in the optical engine.SUMMARY

[0009] According to a first aspect of the present disclosure, an optical engine is provided. The optical engine comprises a heat sink having a first major surface and an opposed second major surface; an electrooptic component having an active area, wherein the electrooptic component is mounted to the first major surface and the active area faces away from the first major surface; and an individually defined optical element situated in an optical path that originates from or terminates in the active area, wherein the individually defined optical element is optically aligned with the active area of the electrooptic component. In some embodiments, the individually defined optical element has a spatially varying index of refraction. In various embodiments, the individuallydefined optical element is configured to reduce divergence of an optical beam emitted by the active area or configured to focus an incident optical beam onto the active area. In some embodiments, the individually defined optical element is configured to pick-off a portion of an optical beam transmitted through it. In various embodiments, the electrooptic component may be a plurality of electrooptic components, each having a corresponding individually defined optical element.

[0010] According to a second aspect of the present disclosure, an optical coupling assembly is provided. The optical coupling assembly comprises a heat sink having a first major surface and an opposed second major surface; an electrooptic component having an active area mounted to the first major surface, wherein the active area faces away from the first major surface; a transparent substrate including an individually defined optical element within or on a surface of the transparent substrate, wherein the individually defined optical element is optically aligned with the active area of the electrooptic component; an optical block aligned with the transparent substrate; and an optical waveguide supported by the optical block in optical communication with the active area. In various embodiments, an optical beam propagates through the optical block between the active area and the optical waveguide. In some embodiments, the optical coupling assembly further comprises a refractive lens situated on a face of the optical block. In various embodiments, the optical waveguide is an optical fiber. In some embodiments, the optical beam is collimated in a region between the transparent substrate and the optical block. In various embodiments, the optical coupling assembly further comprises a reflective surface situated on a face of the optical block. In some embodiments, a plurality of alignment marks are situated on or directly beneath a top surface of the transparent substrate that aid in positioning the optical block on the transparent substrate.

[0011] According to another aspect of the present disclosure, an optical interconnect module is provided. The optical interconnect module comprises an electrooptic component including an active area configured to emit or receive an optical signal; and an individually defined optical element in optical alignment with the active area. In some embodiments, the electrooptic component includes a plurality of active areas and the module further comprises a plurality of individually defined optical elements, wherein each of the plurality of active areas is in optical alignment with an associated individually defined optical element. In various embodiments, the electrooptic component comprises a plurality of electrooptic components. In some embodiments,the individually defined optical element picks-off a portion of an optical beam transmitted through the individually defined optical element, which may be sampled by a monitor photodiode. In various embodiments, the optical interconnect module has a plurality of transmit channels and / or a plurality of receive channels. In some embodiments, a refractive index profile of the individually defined optical element is determined using artificial intelligence.

[0012] According to yet another aspect of the present disclosure, a method of assembling an optical engine is provided. The method comprises mounting an electrooptic component on a first major surface of a heat sink, wherein the electrooptic component has an active area facing away from the first major surface which is configured to emit or detect an optical beam; aligning a processing head of a laser processing tool with the active area; and defining an individual optical element in optical alignment with the active area of the electrooptic component. In various embodiments where the electrooptic component includes a plurality of active areas, an individually defined optical element is defined in optical alignment with each of the plurality of active areas. In some embodiments, the active area is energized during alignment of the processing head, while in other embodiments it is not energized and alignment may occur with a contact ring. In various embodiments, the defined individual optical element collimates an emitted optical beam or focuses a received optical beam. In some embodiments, the defining of the individual optical element is achieved by scanning a focal spot of a processing optical beam emitted by the laser processing tool.

[0013] According to another aspect of the present disclosure, a method of assembling an optical engine is provided. The method comprises mounting an electrooptic component having a plurality of active areas on a first major surface of a heat sink, wherein each active area of the plurality of active areas faces away from the first major surface and is configured to emit or detect a corresponding optical beam; aligning a processing head of a processing tool with a first active area of the plurality of active areas; defining a first individual optical element using the processing tool, wherein the first individual optical element is in optical alignment with the first active area of the electrooptic component; and repeating the aligning and defining steps for each active area of the plurality of active areas. In some embodiments, the electrooptic component is a laser. In variousembodiments where the electrooptic component is a laser, each of the emitted corresponding optical beams is collimated by its corresponding first individual optical element.

[0014] According to yet another aspect of the present disclosure, an optical engine is provided. The optical engine comprises a heat sink having a first major surface; an electrooptic component having an active area and wirebond pads, wherein the electrooptic component is mounted to the first major surface of the heat sink and the active area faces away from the first major surface; wirebonds electrically connected to the wirebond pads; an encapsulant covering at least a portion of the electrooptic component and the wirebonds; a transparent substrate positioned above the electrooptic component such that an optical path between the active area and a location above the transparent substrate passes through the encapsulant and the transparent substrate; and an individually defined optical element situated within the transparent substrate and optically aligned with the active area. In some embodiments, the electrooptic component has a plurality of active areas and the optical engine further comprises a plurality of individually defined optical elements within the transparent substrate, wherein each individually defined optical element is individually defined based at least in part on a position of a corresponding active area.

[0015] According to another aspect of the present disclosure, a method of assembling an optical engine is provided. The method comprises mounting an electrooptic component to top surface of a heat sink, wherein the electrooptic has an active area that faces away from the heat sink; making a wirebond electrical connection to the electrooptic component; encapsulating the wirebonds; mounting the transparent substrate above the wirebonds; aligning a processing head of a processing tool with the active area; and defining an individual optical element using the processing tool, wherein the individual optical element is in optical alignment with the active area of the electrooptic component. In various embodiments where the electrooptic component includes a plurality of active areas, the aligning and defining steps are repeated for each active area to create a plurality of individually defined optical elements.

[0016] According to yet another aspect of the present disclosure, an optical block subassembly is provided. The optical block subassembly comprises an optical block, wherein the optical block has a bottom surface and a side surface configured to transmit an optical beam; a plurality of opticalwaveguides affixed to the optical block; and a plurality of optical elements, wherein each of the plurality of optical elements is associated with a corresponding optical waveguide and a location of each of the plurality of optical elements is individually defined at least in part by a position of each of the optical waveguides. In some embodiments, each optical element is defined on a surface of the optical block by additive manufacturing, such as a refractive lens on the bottom or side surface or a curved mirror on a reflective surface. In various embodiments, each optical element is defined by inducing a spatially localized refractive index change within the optical block. In some embodiments, the plurality of optical waveguides is a plurality of optical fibers arranged as an optical fiber ribbon cable. In various embodiments, the location of each of the plurality of optical elements is individually defined at least in part by a position of an alignment mark or feature on the optical block.

[0017] According to another aspect of the present disclosure, a method of assembling an optical block subassembly is provided. The method comprises affixing a plurality of optical waveguides on an optical block; aligning a processing head of a processing tool with a first optical waveguide of the plurality of optical waveguides; defining a first optical element within or on a surface of the optical block using the processing tool, wherein the first optical element is in optical alignment with the first optical waveguide; and repeating the aligning and defining steps for each optical waveguide of the plurality of optical waveguides In various embodiments, the defining of the first optical element is achieved by scanning a focal spot of a processing optical beam emitted by a laser processing tool. In some embodiments, the defining of the first optical element is achieved by forming a curved mirror on a reflective surface of the optical block or forming a refractive lens on a bottom or side surface of the optical block by an additive manufacturing process.

[0018] According to yet another aspect of the present disclosure, an optical interconnect module is provided. The optical interconnect module comprises an optical engine, wherein the optical engine comprises an electrooptic component and a transparent substrate; an optical block subassembly, wherein an optical waveguide is affixed to the optical block subassembly; and an individually defined optical element, wherein the optical element is configured to help optically couple an optical beam between the electrooptic element and the optical waveguide and the individually defined optical element is defined based at least in part on a position of the electroopticelement or the optical waveguide. In various embodiments, the individually defined optical element is located on a surface of or within the transparent substrate. In other embodiments, the individually defined optical element is located on a surface of or within the optical block of the optical block subassembly. In some embodiments, the optical waveguide is a plurality of optical waveguides, the electrooptic element is a plurality of electrooptic elements, and the individually defined optical element is a plurality of individually defined optical elements. In various embodiments, additive manufacturing or laser processing is used to define the individually defined optical element. In some embodiments, the module further comprises an alignment feature on the optical engine and a mating alignment feature on the optical block subassembly, wherein mating the features places the electrooptic element and the optical waveguide in optical alignment.

[0019] According to another aspect of the present disclosure, an optical coupling assembly is provided. The optical coupling assembly comprises a transparent substrate having a top surface and an opposed bottom major surface; an electrooptic component having an active area configured to emit an optical beam through the transparent substrate or detect an optical beam transmitted through the transparent substrate; an optical block positioned above on the top surface supporting an optical waveguide; a core of the optical waveguide in optical communication with the active area; and an individually defined optical element situated between the electrooptic component and the optical waveguide, wherein a location of the individually defined optical element is based at least in part on a position of the active area or the core of the optical waveguide. In some embodiments, the optical waveguide is a plurality of optical waveguides, the electrooptic component is a plurality of electrooptic components each having an associated active area, and the individually defined optical element is a plurality of individually defined optical elements. In various embodiments, additive manufacturing or laser processing is used to define each individually defined optical element.

[0020] According to yet another aspect of the present disclosure, an optical block subassembly is provided. The optical block subassembly comprises an optical block, wherein the optical block has a bottom surface and a side surface configured to transmit an optical beam; an alignment feature on the side surface configured to mate with an attachable / detachable optical fiber cable; and a plurality of optical elements, wherein each of the plurality of optical elements is configuredto be associated with a corresponding optical waveguide of the attachable / detachable optical fiber cable and a location of each of the plurality of optical elements is individually defined at least in part by a position of the alignment feature.

[0021] According to another aspect of the present disclosure, an optical coupling assembly is provided. The optical coupling assembly comprises a transparent substrate having a top surface and an opposed bottom surface; a plurality of electrooptic components positioned below the bottom, each electrooptic component having an active area; and a plurality of individually defined optical elements situated within or on the top or bottom surface of the transparent substrate, wherein each individually defined optical element is individually aligned with a corresponding active area of the plurality of electrooptic components, such that each individually defined optical element's position is customized based on the position of its corresponding active area independent of the positions of other individually defined optical elements.

[0022] According to yet another aspect of the present disclosure, a method of manufacturing an optical coupling assembly is provided. The method comprises mounting a plurality of electrooptic components to a top surface of a heat sink, each electrooptic component having an active area facing away from the heat sink; for each active area of the plurality of electrooptic components: individually aligning a processing head of a laser processing tool with that active area; and defining an internal optical element within a transparent substrate positioned above the electrooptic element at a position optimized for that specific active area independent of the positions of other internal optical elements, wherein the resulting plurality of optical elements are each individually customized for their corresponding active areas without compromise for alignment with other active areas.

[0023] According to another aspect of the present disclosure, an optical coupling assembly is provided. The optical coupling assembly comprises a transparent substrate having a top surface and an opposed bottom surface; a plurality of electrooptic components mounted to a top surface of a heat sink, each electrooptic component having multiple active areas facing towards the transparent substrate; an optical block positioned above the electrooptic components; a plurality of optical waveguides supported by the optical block; and a plurality of optical elements situatedwithin, on the first surface or on the second surface the transparent substrate, wherein each optical element is individually written and aligned with respect to a corresponding active area after mounting of the electrooptic components and before mounting of the optical block, and the optical elements are configured to provide collimated optical beams in a region between the transparent substrate and optical block to accommodate lateral positioning tolerances between the transparent substrate and optical block while maintaining optical coupling efficiency.

[0024] According to yet another aspect of the present disclosure, a method of manufacturing an optical coupling assembly is provided. The method comprises mounting a plurality of electrooptic components to a top surface of a heat sink, each electrooptic component having multiple active areas; for each active area: determining a position of the active area; aligning a laser processing tool with the determined position; writing a customized optical element within or on a surface of a transparent substrate positioned above the electrooptic component using a processing tool, wherein the customized optical element is configured to provide a collimated optical beam; writing an alignment feature on a surface of or within transparent substrate using the same processing tool while maintaining alignment with the active area; and mounting an optical block supporting optical waveguides above the transparent substrate using the alignment features to achieve registration between the optical block and transparent substrate.

[0025] According to another aspect of the present disclosure, an optical interconnect module is provided. The optical interconnect module comprises an optical engine comprising an electrooptic element including a plurality of active; a wirebond electrical connection; an optical block subassembly comprising a plurality of optical waveguides, wherein each of the plurality of active areas is in optical alignment with an associated optical waveguide of the plurality of optical waveguides; and a plurality of individually defined optical elements, wherein each individually defined optical element of the plurality of optical elements is in optical alignment with an active area and its associated optical waveguide and a position of each individually defined optical element is based on a position of its associated active area independent of the position of the other plurality of active areas. . In some embodiments, the plurality of active areas are situated on a top surface of the electrooptic component and the wirebond electrical connections make contact with the top surface. In various embodiments, an encapsulant covers the plurality of active areas andthe wirebond electrical connections such that optical signals pass through the encapsulant. In some embodiments, the optical engine has an optical engine alignment feature and the optical block subassembly has an optical block subassembly alignment feature aligned to the optical engine alignment feature, potentially via an optical block guide. In various embodiments, the plurality of individually defined optical elements is situated within or on a surface of a transparent substrate positioned above the encapsulant, or within or on a surface of an optical block within the optical block subassembly.

[0026] According to yet another aspect of the present disclosure, an optical engine is provided. The optical engine comprises a heat sink having a first major surface; an electrooptic component having an active area and wirebond pads, wherein the electrooptic component is mounted to the first major surface and the active area faces away from the first major surface; wirebonds electrically connected to the wirebond pads; a transparent encapsulant covering at least the active area and the wirebonds, the encapsulant defining a top surface; and an individually defined optical element situated on the top surface of the encapsulant or within the encapsulant, wherein the individually defined optical element is optically aligned with the active area and situated in an optical path originating from or terminating at the active area through the encapsulant. In some embodiments, the individually defined optical element is situated on the top surface of the encapsulant and may be formed by a surface profile thereof. In other embodiments, the individually defined optical element is situated within the encapsulant and may comprise a region with a modified refractive index. In various embodiments, the optical engine further comprises an alignment feature situated on the top surface of the encapsulant or within the encapsulant.

[0027] According to another aspect, an optical engine is provided comprising a heat sink and an electrooptic component mounted relative thereto. The electrooptic component includes an active area and a substrate, configured such that the optical signal path passes through the substrate of the electrooptic component itself (e.g., a back-emitting VCSEL or back-receiving photodetector). This substrate is substantially transparent at the operating wavelength. An individually defined optical element is situated in this optical path (potentially within or on an overlying transparent substrate or encapsulant) and is optically aligned with the active area specifically via the path passing through the substrate of the electrooptic component.

[0028] According to yet another aspect, a method of assembling an optical engine is provided. The method includes mounting an electrooptic component relative to a heat sink, where the electrooptic component is configured for signal transmission through its own substantially transparent substrate. A processing tool head is aligned with the active area of the component, specifically accounting for this signal path through the substrate of the component. An individual optical element is then defined using the processing tool in this optical path, ensuring alignment with the active area via the path through the substrate of the component.BRIEF DESCRIPTION OF DRAWINGS

[0029] FIG. 1A shows a bottom perspective view of an optical interconnect module according to an embodiment of the present disclosure.

[0030] FIG. IB shows a top perspective view of a portion of an optical interconnect module according to an embodiment of the present disclosure.

[0031] FIG. 2 shows a top surface of an electrooptic component according to an embodiment of the present disclosure.

[0032] FIG. 3A is a cross-sectional view of a portion of a transmit channel of an optical engine according to an embodiment of the present disclosure.

[0033] FIG. 3B is a cross-sectional view of a portion of a receive channel of an optical engine according to an embodiment of the present disclosure.

[0034] FIG. 4A shows a cross-sectional view of a Fresnel zone plate according to an embodiment of the present disclosure.

[0035] FIG. 4B shows a top view of a Fresnel zone plate according to an embodiment of the present disclosure.

[0036] FIG. 5 shows an exemplary refractive index profile of a Fresnel zone plate according to an embodiment of the present disclosure.

[0037] FIG. 6 shows an exemplary refractive index profile of a 1 -dimensional grating according to an embodiment of the present disclosure.

[0038] FIG. 7 is a cross-sectional view of an optical engine according to an embodiment of the present disclosure.

[0039] FIG. 8A shows a cross-sectional view of an internal refractive optical element according to an embodiment of the present disclosure.

[0040] FIG. 8B shows a top view of an internal refractive optical element according to an embodiment of the present disclosure.

[0041] FIG. 9 shows an optical coupling assembly according to an embodiment of the present disclosure.

[0042] FIG. 10 is a cross-sectional view of an optical engine according to an embodiment of the present disclosure.

[0043] FIG. 11 is a cross-sectional view of an optical engine according to an alternative embodiment of the present disclosure.

[0044] FIG. 12 is a cross-sectional view of an optical engine according to an alternative embodiment of the present disclosure.

[0045] FIG. 13 is a cross-sectional view of an optical engine according to another alternative embodiment of the present disclosure

[0046] FIG. 14 is a method of making an optical engine according to an embodiment of the present disclosure.

[0047] FIG. 15 is a cross-sectional view of an optical block subassembly according to an embodiment of the present disclosure.

[0048] FIG. 16 illustrates an optical coupling assembly including an optical block guide according to an embodiment of the present disclosure.

[0049] FIG. 17 illustrates a method of assembling an optical block subassembly according to an embodiment of the present disclosure.

[0050] FIG. 18 is an optical assembly according to an embodiment of the present disclosure.

[0051] FIG. 19 is a cross-sectional view of a composite optical block subassembly according to an embodiment of the present disclosure.

[0052] FIG. 20 is a cross-sectional view of a composite optical block subassembly according to an alternative embodiment of the present disclosure.

[0053] FIG. 21 depicts an optical engine in which an individually defined optical element is defined on a top surface of an encapsulant according to an embodiment of the present disclosure.

[0054] Like reference numbers and designations in the various drawings indicate like elements.DETAILED DESCRIPTION

[0055] The present disclosure can be understood more readily by reference to the following detailed description taken in connection with the accompanying figures and examples, which form a part of this disclosure. It is to be understood that this disclosure is not limited to the specificdevices, methods, applications, conditions or parameters described and / or shown herein, and that the terminology used herein is for the purpose of describing particular embodiments by way of example only and is not intended to be limiting of the scope of the present disclosure. Also, as used herein, the singular forms “a,” “an,” and “the” include “at least one” and a plurality. Further, reference to a plurality as used in the specification including the appended claims includes the singular “a,” “an,” “one,” and “the,” and further includes “at least one.” Further still, reference to a particular numerical value in the specification including the appended claims includes at least that particular value, unless the context clearly dictates otherwise.

[0056] The term “plurality”, as used herein, means more than one. A range of values may be expressed as including all values between a first particular value to a second particular value, including both the first and second values. Similarly, when values are expressed as approximations, by use of the antecedent “about,” it will be understood that the particular value forms another example. All ranges are inclusive and combinable.

[0057] The term “substantially,” “approximately,” and derivatives thereof, and words of similar import, when used to described sizes, shapes, spatial relationships, distances, directions, and other similar parameters includes the stated parameter in addition to a range up to 10% more and up to 10% less than the stated parameter, including up to 5% more and up to 5% less, including up to 3% more and up to 3% less, including up to 1% more and up to 1% less.

[0058] It should be understood that terms such as top, bottom, up, down, right, left, sides, vertical, and horizontal are relative terms and the embodiments described herein can be used in any orientation.

[0059] FIG. 1 A shows a perspective view of a bottom or second surface of an optical interconnect module 100 according to an embodiment of the present disclosure. The optical interconnect module 100 may be configured to mate with an optical fiber cable 102, which may be permanently affixed to the module 100 (commonly referred to as pigtailed to the module) or may be separable from the module 100. The optical fiber cable 102 may be a ribbon cable having a plurality of optical waveguides 112 (later shown in Figs. 9, 15 and 17-19), for example twelve optical fibersdispersed in a row along a lateral or y-direction. The optical waveguides in the optical fiber cable may be oriented along a longitudinal or z-direction. The optical waveguides may be single mode optical fibers or multimode optical fibers. There may be more than one optical fiber cable 102 attached to the optical interconnect module 100, for example, there may be two ribbon cables, one ribbon cable stacked above the other ribbon cable (not shown in FIG. 1 A). In FIG. 1 A a heat sink has been removed to expose an electrooptic component 125 and other elements of the module 100. FIG. 1A shows four electrooptic components, however, there may be any number of electrooptic components 125. In this embodiment, the optical interconnect module 100 is an optical transceiver having two types of electrooptic components 125, a laser 124, which serves as the basis of a transmitter, and a photodetector 126, which serves as the basis of a receiver. In other embodiments, the optical interconnect module 100 may be a transmitter having no receiver elements or a receiver having no transmitter elements. Collectively the laser 124 and photodetector 126 may be referred to as electro-optic (E / O) components 125, since they transform an electrical signal into an optical signal or an optical signal into an electrical signal. Both the laser 124 and photodetector 126 may be comprised of a plurality of individual lasers and photodetectors formed on a single die, each individual laser supporting a transmit channel and each individual photodetector supporting a receive channel. The electrooptic components 125 may be mounted to a heat sink (removed in FIG. 1A). The electrooptic components 125 may be mounted to the heat sink using a placement head of a processing tool, such as a die bonding tool. Optical transmit and receive signals are coupled out of and into the E / O components 125 on a top side of the E / O components, which is not visible in FIG. 1A.

[0060] FIG. IB shows a top perspective view of a portion of the optical interconnect module depicted in FIG. 1A. The E / O components 125 are electrical connected via wirebonds 135. The wirebonds from the laser 124 electrically connect it with the laser driver 119 and the wirebonds 135 from the photodetector 126 electrically connect it with the TIA 122. The laser driver 119 and TIA 122 may also be electrically connected to the printed circuit board 144 via wirebonds. The E / O components 125, laser driver 119, and TIA 122 may all be mounted on a heat sink, most of which is not visible in FIG. IB. Several parts of the heat sink 116 that are visible are optional pillars 167 that extend above the upward extent of the wirebonds 135. The purpose of the pillarsis described below. The heat sink 116 may be formed from a high thermal conductivity metal, such as copper, and may be opaque to optical signals emitted from or received by the E / O components.

[0061] FIG. 2 shows a top surface 130 of a E / O component 125 according to an embodiment of the present disclosure. The top surface 130 of the E / O component 125 may be considered the active face since it contains the emitting / receiving area and the associated electrical connections to that area. The E / O component 125 may be a laser 124, such as a vertical cavity surface emitting laser (VCSEL) or a photodetector. The laser 124 may have a plurality of individual emitting elements 132. In the exemplary laser 124 shown in FIG. 2 there are four individual emitting elements 132; however, there may be any number of individual emitting elements 132. Each individual emitting element 132 may include an active area 134 that transforms an electrical input into an optical output. Surrounding the active area 134 may be an electrically conductive contact ring 136. The contact ring 136 may completely surround the active area 134 as shown in FIG. 2 or it may have one or more discontinuities. In either case it may be said that the contact ring 136 is aligned with and surrounds the active area 134. The active area 134 may be well centered within the contact ring 136, for example, the active area 134 may be centered to within ±0.1, 0.2, 0.5 or 1 microns. The contact ring 136 is configured to inject current into the active area 134 which causes emission of an optical beam from the active area 134. The active area 134 may be part of a VCSEL. Each individual emitting element 132 may also have two wirebond pads 133. One wirebond pad 133 may be in electrical communication with the contact ring 136 through an electrically conductive trace 142 running between them. The other wirebond pad 133 is also in electrical communication with the active area 134 through appropriate doping of the material underlying the top surface 130 and not visible in FIG. 2. The two wirebond pads 133 may be suitable for forming a wirebond electrical connection to the laser 124 and thus may be considered as wirebond pads. The contact ring 136, two wirebond pads 133, and electrically conductive trace 142 may also be formed by patterned metallization of the top surface 130 through a photolithographic process. Since all these elements are metal, these elements are readily visible. The laser 124 may be formed on a GaAs or InP substrate.

[0062] A top surface of a photodetector may be similar in appearance to that of the top surface 130 of the laser 124 shown in FIG. 2. Both the laser 124 and a photodetector may have contactring 136 surrounding the active area 134. A difference between them may be the layout of the wirebond pads 133 and electrically conductive patterning on the top surface. The active areas of laser and photodetector components may also have different physical dimensions that impact coupling tolerances. For laser components, the active emitting area is typically around 10 microns in diameter, while photodetector active areas may be larger, for example, 25-30 microns in diameter. This difference in active area size results in different alignment tolerances between transmit and receive channels, with photodetector coupling generally being more tolerant to misalignment due to the larger active area. This difference in alignment tolerance may influence the positioning of transmit and receive channels within the optical interconnect module. The photodetector transforms an optical input into an electrical output. Current is generated by absorption of an incoming optical beam in the active area 134 and collected by the contact ring 136. The photodetector may be formed on a Si, GaAs, or InGaAs substrate.

[0063] Returning to FIGS. 1A and IB, there may be multiple E / O components 125 in the optical interconnect module 100. Two lasers 124 and photodetectors 126 are shown in FIGS. 1A and IB so there are a total of four E / O components 125 in this embodiment. Since each E / O component 125 may have four individual electrooptic elements (emitters or receivers) (see FIG. 2) there are a total of sixteen optical channels, eight transmit channels and eight receive channels in the module 100 depicted in FIGS. 1A and IB. In other embodiments there may be more or fewer optical channels and the optical channels may be apportioned differently between receiver and transmitter channels. Adjacent to each laser 124 there may be a laser driver 119 and adjacent to each photodetector 126 there may be a transimpedance amplifier (TIA) 122. Collectively, the laser 124, photodetector 126, laser driver 119, TIA 122 may be part of an optical engine, since these components handle conversion of a modulated, high-speed data signal from an optical to electrical signal or an electrical to optical signal. The laser 124 and laser driver 119 may be in electrical communication with each other through wirebonds 135 as shown in FIG. IB. Similarly the photodetector 126 and TIA 122 may be in electrical communication with each other through wirebonds. The E / O components 125 may be exposed through an opening or cutout 143 in a printed circuit board 144. Mounted on the printed circuit board 144 may be a plurality of electrical components, such as a microcontroller 145 that are in electrical communication with the laserdriver 119 and TIA 122. Electrical connections between the printed circuit board 144 and the laser driver 119 and TIA 122 may be made using wirebond electrical connections.

[0064] The optical interconnect module 100 shown in FIGS. 1A and IB may be used as a component in a data transport or optical communication system. Nodes of the communication system, for example, a host and a target, may use a computer bus protocol to send data and auxiliary (control) signals over an optical link. For example, the optical interconnect module 100 may be used to form a data transport system that includes one of the optical interconnect modules coupled to each end of an optical link so that it controls the input and output and hence the transport of data over the optical link. The optical link can comprise any desired optical waveguide, but in an embodiment is a bundle or group of optical fibers, such as the optical fiber cable 102 depicted in FIG. 1A. The information transported to / from the ends of the optical link can be sent and received using separate fibers. As noted above there may be fibers dedicated to transmission and fibers dedicated to reception. Each optical fiber may propagate a single data channel or multiple data channels may be multiplexed into a single fiber using wavelength division multiplexing. While the optical link described herein as an example includes an 8-channel full-duplex optical link using a single optical wavelength in each fiber, the embodiment is not so limited as the optical link may include any number of channels as appropriate to a configuration of the data transport system.

[0065] FIG. 3 A is a cross-sectional view of a transmit portion of an optical engine 108 that may be incorporated into an optical interconnect module, for example, optical interconnect module 100 depicted in FIGS. 1A and IB, according to an embodiment of the present disclosure. An optical beam 104 may be emitted by the laser 124 in a x or transverse direction as part of a transmit channel 160. The laser 124 may be mounted to a first or top major surface 121 of a heat sink 116. The heat sink 116 has an opposed second or bottom major surface 117. The first and second major surfaces 121 and 117 may be flat. The optical beam 104 is emitted in a propagation direction 107 and is transmitted through a transparent substrate 115 emerging from a top surface 129 of the transparent substrate. An optical element 109 may be situated within the transparent substrate 115 in a path of the optical beam 104. The optical element 109 may be considered an internal optical element 106, since the outer surfaces of the transparent substrate are not altered by formation of the internaloptical element 106. The internal optical element 106 is thus formed in the bulk material of the transparent substrate 115, not on any surface of the transparent substrate 115. The optical element 109 may be formed by inducing a localized change in a refractive index in the transparent substrate. The optical element 109 may be refractive or diffractive in nature. In a diffractive optical element, the refractive index spatial is modulated with multiple modulation periods across the optical beam 104, such as in a grating. In a refractive optical element, the refractive index spatial variation is more gradual, such as in a gradient refractive index (GRIN) lens. The optical element 109 may be optically aligned with an active area of the laser 124 (not visible in FIG. 3A). The alignment may be achieved by visualization of the active area 134 or if the active area 134 cannot be directly visualized through visualization of the contact ring 136 or some other feature on the laser 124 (see FIG. 2) The optical element 109 may alter a wavefront of the optical beam 104 as it passes through the optical element 109, thereby changing a divergence of the optical beam 104. In particular, the optical element 109 may reduce the divergence of the optical beam 104 in a region above the top surface of the transparent substrate 115. Advantageously, the optical element 109 may collimate the optical beam 104 emitted through the top surface of the transparent substrate 115. The optical beam 104 may be considered collimated in a region along its propagation path within a Rayleigh length of a beam waist. It may be said that the internal optical element 106 is configured to collimate the optical beam 104 emitted by the active area of the laser 124. As well as collimating the optical beam 104, the internal optical element 106 may be aligned to ensure an optical axis 105 of the optical beam 104 emerging from the top surface 129 of the transparent substrate 115 is oriented to be perpendicular to within a predefined (e.g. manufacturing) tolerance to the top surface 129. The predefined tolerance can be less than 0.05°, 0.1°, 0.2°, or 0.5°.

[0066] Also, shown in FIG. 3 A is a laser driver 119 including a wirebond pad 133. The wirebond pad 133 on the laser driver 119 is electrically connected to a wirebond pad 133 on the laser 124 using a wirebond 135. The term wirebond as used herein refers to both a wirebond, ribbon bond, and any other type of bond in which a thin electrical conductor extends between two flat electrically conductive pads and bonds to those pads by application of heat, pressure, ultrasonic energy, etc. without the use of a bonding agent, such as a solder, conductive adhesive, etc. Wirebonds are used extensively in the electronics industry and highly automated equipment enables fabrication of many wirebonds per second from a single wirebond head. The wirebond135 may be encased in an encapsulant 135 to provide mechanical protection and increase the ruggedness of the wirebond 135. The encapsulant 151 may be transparent and may fill a gap between the transparent substrate 115 and the heatsink 116. As such, the optical beam 104 passes through the encapsulant 151. Although not shown in FIG. 3 A the heat sink 116 may have a pillar (see FIG. IB) extending from the top surface 121 that limits downward motion of the transparent substrate 115 to provide mechanical protection for the wirebonds 135.

[0067] An internal optical element 106 may also be used in a receive portion of an optical engine 308 having a receive channel 162 in which the E / O component is a photodetector 126 as shown in FIG. 3B. The arrangement is as previously described in regard to FIG. 3A so for brevity a description of the common elements will be omitted. A difference between the transmit channel (see FIG. 3A) and receive channel 162 is that the propagation direction 107 of the optical beam 104 is reversed so that the propagation direction 107 is into the transparent substrate 115 along the transverse direction. In the case of the receive channel 162, the optical beam 104 may be collimated in a region adjacent the top surface 129 of the transparent substrate 115 and above the internal optical element 106. The internal optical element 106 may then focus the optical beam 104 on to the active area of the photodetector 126. It should be appreciated that an optical engine, such as the optical engine incorporated into optical interconnect module 100 (see FIGS. 1A and IB), can have both transmit and receive channels. In some embodiments, internal optical elements 106 in the transmit channels may be different than the internal optical elements 106 in the receive channels, while in other embodiments they may be the same. Another difference is that the laser driver 119 of the transmit channel has been replaced by a TIA 122 electrically connected to the photodetector 126 by a wirebond 135.

[0068] The internal optical element 106, such as those shown in FIGS. 3A or 3B, may be formed by laser processing using a laser processing tool. Specifically, a laser, such as an ultrafast laser generating a train of picosecond or femtosecond long pulses may be focused into the transparent substrate 115. At regions at and / or near the focus, an intensity of the pulse may induce a permanent change in the optical properties of the material forming the transparent substrate 115. A magnitude of the permanent change may be proportional to an energy in each laser pulse of the processing beam pulse train. The permanent change may be a change in the index of refraction. Alternatively,the permanent change may be a change in the material absorption or scattering. By scanning the focal position of the processing laser beam emitted by the laser processing tool within the transparent substrate 115, the internal optical element 106 can be written or formed. It should be understood that certain laser processing techniques, such as those that build up material through polymerization processes, are considered forms of additive manufacturing as described further below. The pulse energy and focal spot size of the processing laser beam may be adjusted as well to tailor the optical properties of the internal optical element 106. It should be appreciated that other types of laser processing, for example, using crossed laser beams may be used to write or define the internal optical element 106. The crossed beams may give rise to an interference pattern, which may be used to define the internal optical element 106. In some embodiments, the internal optical element 106 may be a computer-generated hologram. Artificial intelligence may be used to determine the desired spatial variation of the refractive index and the laser processing parameters needed to generate the desired spatial variation in the refractive index that creates the internal optical element 106. The internal optical element 106 may be a blazed grating.

[0069] The spatial distribution and depth of refractive index modulation can be precisely controlled during the writing process. For laser-written optical elements, the magnitude of the permanent change may be proportional to the energy in each laser pulse. The processing parameters including pulse energy, focal spot size, and scanning pattern may be optimized for each optical element individually. This individual optimization allows each optical element to be customized for its specific channel, taking into account the position and characteristics of both the electrooptic component and the optical waveguide

[0070] In addition to the depth of refractive index modulation a thickness, or more generally a spatial distribution, of the refractive index modulation will also impact the differential phase shift acquired across a wavefront of the optical beam 104 as it propagates in the propagation direction 107 through the optical element 106. The spatial distribution of the refractive index modulation and the modulation depth can be varied in a coordinated manner to achieve a desired change in the optical beam 104 wavefront resulting in a collimated beam for the transmit channel 160 or a focused beam for the receive channel 162.

[0071] An example of a laser processing method is the SCRIBE (Subsurface Controllable Refractive Index via Beam Exposure) method described by Corey A. Richards, et. al. in a paper entitled “Hybrid achromatic microlenses with high numerical apertures and focusing efficiencies across the visible” published in Nature Communications (2023) 14:3119. This paper describes a method to induce a spatially localized refractive index variation in a transparent substrate. The method can produce both refractive and diffractive internal optical elements. The internal optical elements are formed in a PSiO; or PiS substrate, which is a porous SiCh or Si structure, respectively, in which the pores are filled with photoresist. The substrate is mechanically fragile and is attached to a fused silica substrate for subsequent processing and handling. A focused femtosecond laser is used to polymerize the photoresist by nonlinear polymerization at specific locations in the PSiCh or PiS. The nonlinear polymerization may be a two photon polymerization. The processing laser beam is scanned in a desired volumetric pattern to form internal optical elements. Unpolymerized photoresist is removed from the pores by developing the processed substrate. An advantage of the SCRIBE fabrication method is that the induced refractive index variation between the laser processed and unprocessed substrate may be large relative to other laser processing techniques. However, any laser processing method may be used to write or define the internal optical elements described herein.

[0072] The position of the laser processing beam may be controlled by a processing head of a laser processing tool. Specifically, the processing head may direct the laser processing beam so that the internal optical element is aligned with an active area of an E / O component. The internal optical element written by the laser processing tool is thus individually aligned with each active area.

[0073] The internal optical element 106 of FIGS. 3A-3B may be a diffractive internal optical element, such as a Fresnel zone plate 146 as shown in FIGS. 4A and 4B. Additionally, the optical element can be a refractive optical element, depending on the system requirements. In some embodiments, a combination of both diffractive and refractive optical elements may be used to improve or optimize optical performance.

[0074] FIG. 4A shows a cross-sectional view of the Fresnel zone plate 146 and FIG. 4B shows a top view of the Fresnel zone plate 146. A coordinate axis may be defined with the bottom surface127 of the transparent substrate 115 being in a horizontal y-z plane and a vertical x-axis extending upward from the bottom surface 127 of the transparent substrate 115. The z-axis may define a longitudinal direction, the y-axis may define a lateral direction, and the x-axis may define a height or transverse direction. The x-axis may define a center of the Fresnel zone plate 146 and it may be radially symmetric about the x-axis. A vertical center of the Fresnel zone plate 146 may be a height, h, from the bottom surface 127 of the transparent substrate 115. The Fresnel zone plate 146 may include a series of concentric rings or zones of varying width. There may be two types of zones, a first zone type 148, and a second zone type 150, with each zone type having different optical properties. The first zone type may include a central zone 152. Advantageously, both the first and second zone types 148, 150 may be transparent, but have a different index of refraction, An. Having both zone types 148 and 150 transparent helps maximize optical transmission through the Fresnel zone plate 146. A zone height, hz, may be arranged such that an optical beam transmitted through the Fresnel zone plate 146 experiences a phase shift of approximately it between portions of the optical beam passing through the first zone 148 and those portions passing through the second zone 150. The width and spacing of the first and second zones 148, 150 may be chosen such that a diverging wavefront of an optical beam incident on the Fresnel zone plate is collimated by the Fresnel zone plate 146. Similarly, a collimated beam incident on the Fresnel zone plate 146 may be focused by the Fresnel zone plate. As previously disclosed, the Fresnel zone plate 146 may be situated within the transparent substrate 115.

[0075] As disclosed above in the description of FIGS. 4A and 4B, the refractive index of the material forming the transparent substrate 115 may be permanently changed in a spatially localized manner having two zones with a different refractive index For example, FIG. 5 depicts a representative refractive index profile 154 for the Fresnel zone plate depicted in FIGS. 4A and 4B. The refractive index profile 154 may vary in a modulated, stepwise manner from a base value, nb, which corresponds to the refractive index of the unprocessed material constituting the transparent substrate 115, to a processed value, nb+An. Here An represents a magnitude of the refractive index change induced by the laser processing. The refractive index change shown in FIG. 5 is positive, but the refractive index change in the processed zone may be negative.

[0076] It should be appreciated that the internal optical element 106 need not have two distinct zones with a different refractive index, but rather may consist of a discrete number of refractive index levels or a continuous variation in the refractive index across the internal optical element. Using a refractive index profile having multiple discrete levels or a continuous variation may result in an internal optical element 106 that is more efficient than an internal optical element 106 employing only a binary change in the refractive index. FIG. 6 depicts an exemplary index profile 154 having a continuous variation in the refractive index. This profile has a sinusoidal refractive index modulation as a function of the longitudinal position. The internal optical element 106 may have a uniform spacing, s, between successive maxima in the refractive index. The maximum magnitude of the refractive index change from its base value is Anmax. The refractive index may be uniform over the internal optical element in the lateral direction, such that the internal diffractive optical element forms a 1 -dimensional grating. Such an internal diffractive optical element may be used as a beam splitter to pick off part of the optical beam 104 (see FIG. 7). Generally, a grating will produce two picked-off beams, one on each side of the main optical beam 104, with the angle of the picked-off beam dependent on the grating spacing, s. A blaze or bias may be added to the refractive index profile 154 so that picked-off beams on opposite sides of the main beam have a different power level. It should be appreciated that the longitudinal scale may not be the same between FIG. 5 and FIG. 6.

[0077] FIG. 7 is a cross-sectional view of a portion of an optical engine 108 according to an embodiment of the present disclosure having a plurality of optical elements in the transparent substrate 115. Many of the features of the optical engine 108 depicted in FIG. 7 are similar to those described above relative to FIG. 3 A and will not be repeated here for brevity. In addition to those features previously described, the optical engine 108 may have a plurality of optical elements, such as two optical elements, a first optical element 106a and a second optical element 106b. The two optical elements 106a and 106b may be arranged in series, such that the optical beam 104 passes through both internal optical elements 106a and 106b As depicted in FIG. 7 the first internal optical element 106a may collimate the optical beam 104 emitted by the laser 124. The first internal optical element 106a is shown as a Fresnel zone plate in FIG. 7, but in other embodiments may be an internal refractive optical element. The second internal optical element 106b may pick-off a portion of the optical beam 104 to form a picked-off optical beam 156. Preferably the secondinternal optical element may be a 1 -dimensional grating It should be appreciated that the first and second internal optical elements 106a, 106b are not limited to a Fresnel zone plate and a 1- dimensional grating but can be any type of diffractive or refractive internal optical element.

[0078] The picked-off optical beam 156 may be detected by a monitor photodiode (not shown in FIG. 7). It may be advantageous to mount the monitor photodiode on the top surface 121 of the heat sink 116, so it is situated in the same horizontal plane as the laser 124. This arrangement may be achieved by reflecting the picked-off optical beam 156 off the top surface 129 of the transparent substrate 115 (reflection not shown in FIG. 7). Each transmit channel may have an associated monitor photodiode.

[0079] The internal optical elements depicted in FIGS. 4A, 4B, 5, 6 and 7 may all be considered to be diffractive internal optical elements, since the refractive index has multiple modulation periods across the internal optical element. As described above, in some embodiments the internal optical element may be a refractive optical element. FIGS. 8 A and 8B depict a refractive index profile associated with an exemplary internal refractive optical element FIG. 8A shows a cross- sectional view of an internal refractive optical element 176 according to an embodiment of the present disclosure. FIG. 8B shows a top view of the internal refractive optical element 176 according to an embodiment of the present disclosure. FIGS. 8A and 8B are similar to FIGS. 4A and 4B, which depict an internal diffractive optical element, and for brevity a description of common features between the figures will not be repeated. The z-axis may define a center of the internal refractive optical element 176 and the internal refractive optical element 176 may be radially symmetric about the z-axis. A vertical center of the internal refractive optical element 176 may be displaced a height, h, from a bottom surface 127 of the transparent substrate 115. The internal refractive optical element 176 may comprise two types of zones, a first zone 178, and a second zone 180, with each zone having a different, substantially uniform refractive index. The first zone 178 may correspond to unprocessed regions of the transparent substrate 115 and the second zone 180 may correspond to a laser processed region. The refractive index difference between the first zone 178 and second zone may be An. The internal refractive optical element 176 may have a maximum thickness, t, and both its top surface 182 and bottom surface 184 may be curved. The thickness and curvature of first zone 178 and the refractive index difference betweenthe first zone 178 and second zone 180 may be chosen such that a diverging wavefront of an optical beam incident on the internal refractive optical element is collimated by the internal refractive optical element 176. Similarly, a collimated beam incident on the internal refractive optical element 176 may be focused by the internal refractive optical element. As previously disclosed, the internal refractive optical element 176 may be situated within the transparent substrate 115 between the top surface 129 and the bottom surface 127 of the transparent substrate 115.

[0080] FIGS. 8A and 8B depict a refractive optical element 176 formed by having an interface within the transparent substrate 115 between a first zone 178 having a first refractive index and a second zone 180 having a second refractive index different than the first refractive index. The refractive optical element 176 may be a lens. It should be appreciated that a refractive lens can be formed with the transparent substrate by defining a gradient refractive index (GRIN) lens within the transparent substrate In this embodiment, the refractive lens is formed by a gradient in the refractive index along the y- and x-directions. Thus, rather than having two distinct zones with a different refractive index, a GRIN refractive lens may have a continuously varying refractive index across the lens. A GRIN lens that causes an optical beam passing through it to converge will have a higher refractive index at the center of the lens and a GRIN lens that causes an optical beam passing through it to diverge will have a lower refractive index at the center of the lens.

[0081] It should be appreciated that the stepwise behavior in the refractive index profile depicted in FIG. 5 and the sinusoid behavior depicted in FIG. 6 are only two examples of a refractive index profile that may be used. The internal optical element 106 need not lie in a plane but may curve. More generally, the refractive index profile can vary in a complex manner in all three directi ons / dimensions, the longitudinal direction, the lateral direction, and the transverse direction, as shown in FIGS. 3 A and 3B. As disclosed above, more than one internal optical element may be situated within the transparent substrate 115. The optical beam 104 (see FIG. 7) may first pass through a first internal optical element 106a and then pass through a second internal optical element 106b. Such complex tailoring of the refractive index profile of one or more internal optical elements 106 may allow shaping a transverse beam profile of the optical beam 104 in any desired manner. For example, it may be advantageous to have a toroidal beam profile as described in moredetail below. In some embodiments, a desired refractive index profile may be determined by using artificial intelligence to generate a desired optical intensity profile in the optical beam 104.

[0082] An example of a transverse beam profile that may be generated using a diffractive internal optical element is a transverse beam profile having a toroidal energy distribution. The toroidal energy distribution may have a depressed power level at the center of the optical beam and a radially symmetric higher power level ring surrounding the depressed central area. When this transverse beam profile is launched into a multimode optical fiber, it will primarily excite skew modes in the optical fiber. Advantageously, such a transverse beam profile may propagate down the optical fiber with less modal dispersion than a typical Gaussian power distribution. It should be appreciated that a toroidal beam profile is only one example of an optical beam characteristic that may be achieved with an internal optical element.

[0083] The collimation of the optical beam in the region between the transparent substrate and optical block provides important manufacturing advantages beyond basic optical coupling. When the beam is collimated in this region, the optical coupling becomes significantly more tolerant to lateral misalignment between the transparent substrate and optical block. Even if these components are slightly misaligned laterally, a collimated beam will still focus to substantially the same position on the optical waveguide core for a transmit channel and the photodetector active area for a receive channel, maintaining coupling efficiency between the optical waveguide and E / O component despite possible positional misalignment.

[0084] This tolerance to misalignment occurs because the focal point produced by the refractive lens on the optical block is substantially independent of the lateral position of the collimated beam incident on the lens. While the focal spot position is relatively insensitive to beam position, it remains sensitive to the angle of incidence of the beam on the refractive lens. The individual alignment of each internal optical element helps ensure each optical beam has a perpendicular or substantially perpendicular angle of incidence on its corresponding refractive lens, optimizing coupling efficiency across all channels without requiring perfect lateral alignment between components.

[0085] FIG. 9 shows a cross-sectional view of an optical coupling assembly 110 between an E / O component 125 and an optical waveguide 112 according to an embodiment of the present disclosure. While only a single optical channel is shown in FIG. 9 there may be a plurality of optical channels in the optical coupling assembly 110. The optical coupling assembly 110 places the optical waveguide 112 in optical communication with the active area (not visible in FIG. 9) of the E / O component 125. The optical beam 104 may propagate through an optical block 118 between the active area of the E / O component 125 and an end face 170 of the optical waveguide 112. The optical coupling assembly 110 may include the optical engine 108 as previously described and depicted in FIGS 3 A. The optical engine 108 may include a transparent substrate 115, an internal optical element 106, and an E / O component 125 as previously described. Additionally, the optical coupling assembly 110 may include the optical block 118. The optical coupling assembly may also include the optical waveguide 112, which may be an optical fiber. The optical waveguide 112 may be mounted to the optical block 118. The optical block 118 may be mounted to the top surface 129 of the transparent substrate 115. A bottom surface 168 of the optical block 118 may face the top surface 129 of the transparent substrate 115 and may include a refractive lens 158. In a transmit channel, the refractive lens 158 is configured to focus the optical beam 104 into the optical waveguide 112. In a receive optical channel, the refractive lens 158 is configured to collimate the optical beam 104 in a region between the optical block 118 and transparent substrate 115. The refractive lens 158 may be situated adjacent and parallel to the top surface 129 of the transparent substrate 115. Alternatively, the refractive lens 158 may be situated on a side surface 166 of the optical block 118 facing the optical waveguide 112. The optical block 118 may also include a reflective surface 114. The reflective surface 114 serves to redirect the optical beam 104. Both the side surface 166 and reflective surface 114 may be flat.

[0086] In some embodiments, the optical beam 104 may be collimated in a region between the internal optical element 106 and the refractive lens 158 in a transmit channel. The optical beam 104 may be considered collimated in a region along its propagation path within a Rayleigh length of a beam waist An advantage of this arrangement is that optical alignment of the E / O component 125 with the optical waveguide 112 is relatively insensitive to the placement of the optical block 118 on the top surface 129 of the transparent substrate 115. This behavior arises from the position of the focus produced by the refractive lens 158 being substantially independent of the position ofthe optical beam 104 on the refractive lens 158. While the focal spot position is insensitive to optical beam 104 position, it is sensitive to an angle of incidence of the optical beam 104 on the refractive lens 158. Individual alignment of the internal optical element 106 in each channel of the optical coupling assembly 110 helps to ensure that the optical beam 104 will have a perpendicular or substantially perpendicular angle of incidence on the refractive lens 158.

[0087] For a receive channel, the refractive lens 158 may collimate the optical beam 104 and the internal optical element 106 may focus the optical beam 104 on tothe E / O component 125. Optical alignment of the receive channel may be less sensitive than a transmit channel, since the active area of a VCSEL is often smaller than the active area of a photodetector.

[0088] As disclosed above, the optical coupling assembly 110 may include a plurality of optical channels. The optical block 118 may be a monolithic structure that includes a plurality of refractive lens 158 with each optical channel having its associated refractive lens 158. If the optical block 118 is formed by a molding process, a spacing between each refractive lens 158 is fixed. Thus, when the optical block 118 is aligned with the E / O component s) 125 alignment for each channel cannot be individually optimized. The final alignment will represent a compromise in the optical block 118 alignment which provides the best overall alignment. An advantage of individually defining, or more generally defining, each internal optical element 106 is that alignment of each internal optical element can be optimized. As a result, the optical coupling assembly 110 may be more tolerant of lateral misalignment of the optical block 118.

[0089] A net result of using the internal optical element 106 in both transmit and receive channels is that the optical interconnect module 100 may have a larger tolerance window for placement of the optical block 118 on the transparent substrate 115, which in turn may reduce the manufacturing cost. Also, the optical interconnect module 100 may operate over a wider temperature range, since the transmit and receive optical channels will remain aligned despite dimensional changes caused by varying the operating temperature. In some embodiments, passive alignment of the optical block 118 may be achieved by placing alignment features on the optical block 118 that mechanically engage with mating features on the transparent substrate 115 or some other element of the optical interconnect module 100 (not shown in FIG. 9).

[0090] The optical waveguide 112 may be either a multimode or single mode optical fiber. For multimode fibers, the angular acceptance cone for incoming light is generally larger than for single mode fibers, providing more tolerance for angular misalignment. Single mode fibers require more precise alignment but can support higher bandwidth applications. The individually optimized alignment of each internal optical element 106 can help achieve the tighter alignment tolerances required for efficient coupling into single mode fibers. This capability to achieve precise alignment for single mode fibers represents a significant advantage over conventional approaches that rely on simultaneous alignment of multiple channels.

[0091] Passive alignment may be achieved by using relatively inexpensive, low-precision capital equipment (for example, approximately ± 10 pm tolerance) that places elements to be aligned in contact or proximity to each other and allows mechanical features on the mating elements to register with each other. Passive alignment contrasts with active alignment, which requires expensive, high-precision capital equipment or tooling that enables alignment to approximately ± 1 pm tolerance or better.

[0092] FIG. 9 depicts a specific arrangement of internal optical elements between the E / O component 125 and optical waveguide 112, that is a first optical element 109 within the transparent substrate 115 and a second optical element 159 on the bottom surface 168 of the optical block 118. The first optical element 109 may be an internal optical element 106 as previously described. The second optical element 159 may be considered a surface optical element, since the optical power of the second optical element 159 arises in part from the topology of the surface on which the second optical element 159 is formed. In FIG. 9 the second optical element 159 is depicted as a refractive lens 158. The first and second optical elements 109 and 159 arrangement depicted in FIG. 9 enables efficient optical coupling between the E / O component 125 and optical waveguide 112. However, in other embodiments the optical elements can be of different types, numbers, and positions in addition to those depicted in FIG. 9. Any surface through which the optical beam 104 propagates may include a surface optical element. These surfaces may include the top surface 129 of the transparent substrate 115 and the bottom surface 168 and side surface 166 of the optical block. Any reflective surface, such as reflective surface 114, may be curved instead of flat to provide optical power. Any transparent material through which the optical beam 104 propagatesmay have an internal optical element that impacts optical beam propagation. For example, rather than having two optical elements in the optical beam 104 between the E / O component 125 and optical waveguide 112 only a single optical element may be used or more than two, such as three or four, optical elements may be used. Specific examples of these various optical element arrangements are described in more detail below.

[0093] FIG. 10 is a cross-sectional view of an optical engine 108 according to an embodiment of the present disclosure that depicts one of the many possible arrangements. Many of the features of the optical engine 108 are similar to those described above relative to FIG. 3 A and will not be repeated here for brevity. In addition to those features already previously described the optical engine 108 may include a surface optical element 163, such as a refractive lens 120, situated on the top surface 129 of the transparent substrate 115. The refractive lens 120 may be formed by an additive manufacturing process directly on to the top surface 129 of the transparent substrate 115. The additive manufacturing process may be a two-photon polymerization printing process, which is a type of laser processing technique whereby the focused laser induces polymerization only at the focal point, allowing precise, layer-by-layer building of structures. The refractive lens 120 may be formed of a polymer or glass. A combination of the internal optical element 106 and refractive lens 120 may serve to collimate the optical beam in a region immediately above the refractive lens 120 for a transmit channel and focus the optical beam for a receive channel. Although not shown, in some implementations the refractive lens 120 may be situated on the top surface 129 of the transparent substrate 115 without the use of the internal optical element 106.

[0094] FIG. 11 is a cross-sectional view of an optical engine 108 according to an alternative embodiment of the present disclosure. Many of the features of the optical engine 108 are similar to those described above relative to FIG. 3A and will not be repeated here for brevity. The embodiment shown in FIG. 11 differs from the previously described embodiments in that the transparent substrate 115 includes a plurality of transparent substrates, a first transparent substrate 113a and a second transparent substrate 113b. Unlike previously described embodiments in which the transparent substrate 115 was a monolithic structure, in this embodiment the transparent substrate 115 is a composite structure. Each of first 113a and second 113b transparent substrates may take the form of a rectangular parallelepiped. The first 113a and second 113b transparentsubstrates may be bonded together to form a unitary structure. The first transparent substrate 113a may form the bottom or second surface of the transparent substrate 115. The second transparent substrate 113b may form the top or first surface of the transparent substrate 115. The first transparent substrate 113a may be arranged to have desirable thermal and mechanical properties suitable for facing the E / O component 125. It may be said that the first transparent substrate 113a has superior mechanical properties compared to the second transparent substrate 113b. For example, the first transparent substrate 113a may have a lower coefficient of thermal expansion, may have a higher toughness, and may be more rigid than the second transparent substrate 113b. The second transparent substrate 113b may be arranged to have desirable optical properties suitable for defining an internal optical element 106 within the second transparent substrate 113b. In particular, large spatially localized differences in the refractive index of the second transparent substrate 113b may be induced by exposure to laser illumination. For example, the second transparent substrate 113b may be formed from porous silicon dioxide in which the pores are filled with a polymer, photoresist, or other transparent material that undergoes a physical or chemical change when exposed to laser illumination. The second transparent substrate 113b may take the form of a thin film having a thickness less than 0.5 mm. In some embodiments, the relative position of the first and second transparent substrates may be interchanged. Additionally, the transparent substrate 115 may be a unitary structure comprising three individual substrates bonded together, with the central substrate having desirable properties for defining an optical element and the other substrates having desirable mechanical properties.

[0095] FIG. 12 is a cross-sectional view of a transmit channel 160 of an optical engine 108 according to an alternative embodiment of the present disclosure. Many of the features of the optical engine 108 are similar to those described above relative to FIG. 3 A and will not be repeated here for brevity. FIG. 12 shows the optical element 109 as an internal optical element 106; however, the optical clement 109 may be either an internal optical element, a surface optical element, or there may be a plurality of optical elements within and / or on the transparent substrate 115. The embodiment shown in FIG. 12 differs from the previously described embodiments in that the transparent substrate 115 includes alignment features 164. The alignment features 164 may be located on or immediately adjacent to the top surface 129 of the transparent substrate 115. The alignment features 164 may be formed during the same manufacturing step as the internal opticalelement 106. Alternatively, the alignment features 164 may be formed in a bulk manufacturing process, such as but not limited to, photolithography and molding, prior to the mounting of the E / O component 125. The alignment features may be fiducial marks or they may be mechanical features that modify a surface profile of the top surface 129, such as a cleat or depression. Thus, the alignment features 164 may be accurately registered with respect to the optical element 109, for example, within a tolerance of + / - 0.1, 0.2, 0.5, or 1 micron. An advantage of the alignment features 164 being on or near the top surface 129 is that they may be readily detected by a placement tool used to position an optical block 118 (see FIG. 9) onto the top surface 129 of the transparent substrate 115. In some embodiments, the alignment features 164 may mechanically register the optical block 118 to the transparent substrate 115. As previously described, the required placement accuracy of the optical block 118 to the transparent substrate 115 may be much larger, for example, ± 10, 20 or 30 microns, as compared to the required placement accuracy of each individual optical element 109 relative to the active area 134 of each E / O component 125.

[0096] A receive channel of the carrier subassembly 108 may be similarly arranged with a photodetector substituted for the laser 124 and the propagation direction 107 reversed.

[0097] FIG. 13 is a cross-sectional view of an optical engine 108 according to an alternative embodiment of the present disclosure. FIG. 13 is similar to FIG. 12, except that rather than an internal optical element being defined with the transparent substrate 115, a surface optical element 163 is defined on the top surface 129 of the transparent substrate 115. The surface optical element 163 may be a first refractive lens 120. During the same manufacturing step used to define the surface optical element one or more alignment features 164 may be defined on the top surface 129 of the transparent substrate 115. The alignment features may take the form of a raised area with a recess 165. The recess 165 may be configured to mate with a cleat on an optical block (not shown in FIG. 13). An optical block with cleats is described in Patent Cooperation Treaty Publication No. WO2024243512, which is incorporated by reference as if set forth in its entirety herein. Using the same processing tool in the same manufacturing step to define both the first refractive lens 120 and the alignment features 164 helps ensure accurate registration between these features.

[0098] FIG. 14 is a method 200 of making an optical engine according to an embodiment of the present disclosure. At a first step 202, an E / O component may be mounted to a first or top major surface of a heat sink. In some embodiments, the E / O component may have a plurality of active areas. In some embodiments, a plurality of E / O components may be mounted to the first major surface in step 202. The E / O component(s) may be oriented so that all active areas of the E / O component(s) face away from the first major surface of the transparent substrate. As described above, each active area may have a contact ring that surrounds or substantially surrounds each active area of the E / O component electrically connected to wirebond pads on the E / O component. In step 204, wirebond electrical connections are made to wirebond pads of the E / O component. In step 206, the wirebonds are encapsulated in a transparent encapsulant to provide mechanical protection for the wirebonds. The encapsulant may also cover the active areas. In step 208, a transparent substrate is mounted on top of the encapsulant. In step 210, a processing / placement head of a processing tool may accurately align with an active area on the E / O component. The processing tool may remove material from, add material to, or modify the physical properties of the transparent substrate at desired locations within or on the surface of the transparent substrate. The processing tool may be a laser processing tool, an additive manufacturing processing tool, or some other type of processing tool capable of defining an optical element. Alignment may be achieved by either adjusting a position of a processing head, adjusting a position of the transparent substrate, adjusting a position of an intervening element in the processing tool situated between the transparent substrate and the processing head or some combination of these adjustments. In step 212, the processing tool may write or define an optical element within or on the top or first major surface the transparent substrate that is accurately aligned with the active area of the E / O component. The optical element can be a surface optical element or an internal optical element. The processing tool may define a plurality of optical elements that are serially arranged in a single optical channel. As disclosed above, an E / O component may have a plurality of active areas and a corresponding optical element(s) may be written for each active area. Importantly, each optical element is aligned individually with each active area, so no compromise in alignment is required as may be the case if a plurality of active areas are simultaneously aligned with a plurality of optical elements. If there are a plurality of E / O components each active area of each E / O component may have a corresponding optical element(s) written in turn. As such each individually defined optical element's position is customized based on the position of its corresponding activearea independent of the positions of other individually defined optical elements. In step 214, a decision is made whether an optical element(s) has been written for all active areas on all electrooptic components that are mounted to the heat sink. If not, the method returns to step 210 where the processing head is aligned with another active area and the defining step 212 is repeated. If the decision in step 214 is a yes, indicating that all active areas have had corresponding optical elements written, the method 200 proceeds to step 216 which may represent a completed optical engine. The optical engine may then be integrated into an optical coupling assembly and further integrated into an optical interconnect module as described above.

[0099] It may be said that in an embodiment of the present disclosure a method is described for assembling an optical engine. In a first step an electrooptic component having a plurality of active areas is mounted on a first major surface of a heat sink. Each of the plurality of active areas which is configured to emit or detect an optical beam that propagates away from or towards the active area. In a second step, wirebond electrical connections are made to wirebond pads adjacent the active area. In a third step, the wirebonds are encapsulated. In a fourth step, a transparent substrate is mounted on top of the encapsulant. In a fifth step, a processing head of a processing tool is aligned with a first active area of the plurality of active areas. A first optical element is then written within or on the transparent substrate such that the first optical element is in optical alignment with the first active area of the electrooptic component. The aligning and defining steps are then repeated for each active area of the plurality of active areas.

[0100] One feature of method 200 is that an optical element is aligned with each active area individually. Thus, each active area may be said to have a corresponding optical element which is individually aligned with its corresponding active area. The defining of the optical elements may occur in a sequential manner, with a first optical element written corresponding to a first active area, a second optical element written corresponding to a second active area, and so on, until each active area has a corresponding optical element. It should be appreciated that multiple processing heads may be used to fabricate a single optical engine. In this case, a plurality of optical elements may be written simultaneously, but each optical element will be aligned with its corresponding active area.

[0101] An advantage of the method 200 is that an optical element may be aligned to each active area individually. This contrasts with many prior art systems that have multiple active areas on a single die in which a single optic having multiple refractive lenses is aligned with all active areas simultaneously. This inevitably results in a compromise in alignment of any individual active area to its corresponding refractive lens. By individually aligning the optical element to each active area, higher coupling efficiency between the E / O component and the optical waveguide may be achieved for all active areas on the E / O component. During the alignment process the E / O component may be energized so that optical alignment between an individually defined optical element and an active area can be achieved without reference to a contact ring or any other marking on the E / O component. Alternatively, the E / O component may not be energized and optical alignment between an optical element and an active area may be achieved by aligning to the inactivated active area, contact ring, or some fiducial mark on the E / O component.

[0102] The E / O component has generally been described as either a VCSEL having multiple individual emitters or a photodetector having multiple individual detectors; however, the E / O component is not so limited. In particular, the E / O component may be a photonic integrated circuit, such as, but not limited to, a silicon photonics integrated circuit. The driver and TIA may be integrated into the photonics integrated circuit, or the driver and TIA may be separate components. In some embodiments, the driver and TIA may be combined into a separate component which is placed in electrical communication with the photonic integrated circuit. The photonic integrated circuit may include a plurality of individual emitters and a plurality of individual detectors. In some embodiments, the photonic integrated circuit may only include emitters and the photodetectors may be on a separate component.

[0103] The above description is generally directed to mounting an E / O component prior to defining an optical element, but the invention is not so limited. In an alternative embodiment, a plurality of optical elements may be written either within or on top surface of a transparent substrate. A placement head of a die bonding tool may then be aligned with the plurality of optical elements. An electrooptic component having a plurality of active areas may be mounted on the first major surface of the heat sink with the placement head. Each active area of the plurality of active areas is configured to emit or detect a corresponding optical beam that propagates throughthe transparent substrate and each of the plurality of active areas is in optical alignment with each of the plurality of optical elements.

[0104] The previous description has been chiefly directed towards defining an optical element within or on a surface of a transparent substrate that is part of an optical engine that supports an E / O component; however, the present invention is not so limited. As noted above, an optical element can also be defined within or on a surface of the optical block. Embodiments of the current invention that define an optical element on the optical block will now be described.

[0105] FIG. 15 depicts a cross-sectional view of an optical block subassembly 198. The optical block subassembly 198 includes an optical block 118 having a permanently attached, i.e. pigtailed, optical waveguide 112. An optical axis 105 extends through the optical block 118. The optical axis 105 traverses two surfaces, a bottom surface 168 and a side surface 166. Additionally, the optical axis 105 may have its orientation changed by intersecting a reflective surface 114. An optical element may be defined in any of five different regions within or on a surface of the optical block 118. A surface optical element 186 may be defined on the side surface 166 of the optical block 118. A surface optical element 188 may be defined on the bottom surface 168 of the optical block 118. The surface optical elements 186, 188 may be diffractive or refractive optical elements. A surface optical element 190 may also be formed on the reflective surface 114. The surface optical element 190 may be a diffractive or reflective optical element. An internal optical element 192 may be formed along the optical axis 105 in a region between the bottom surface 168 and the reflective surface 114. The internal optical element 192 may be a diffractive or refractive optical element. An internal optical element 194 may be formed along the optical axis 105 in a region between the side surface 166 and the reflective surface 114. The internal optical element 194 may be a diffractive or refractive optical element.

[0106] The optical block 118 may include a waveguide support portion 196 arranged to support an optical waveguide 112, such as an optical fiber. The waveguide support portion 196 may support a plurality of optical waveguides 112 arranged in a row along the lateral direction (not visible in FIG. 15, see FIG. 1). The optical waveguides 112 may be mechanically connected to each other and mounted on the waveguide support portion 196 in a single processing step. Eachoptical waveguide 112 may have an optical waveguide core. Each optical waveguide core may transmit optical signals along its length as part of an optical channel. The optical waveguide cores may be spaced at a regular pitch, such as 250 microns between adjacent waveguide cores. In an embodiment, the optical waveguides 112 may be mounted to the waveguide support portion 196 of the optical block 118 prior to definition of an optical element 186, 188, 190, 192, 194 within or on a surface of the optical block 118. Each optical element 186, 188, 190, 192, 194 may be individually defined with respect to an associated optical waveguide core mounted on the optical block 118. Thus, each optical channel traversing the optical block 118 can be individually aligned and optimized. Advantageously, individual alignment of the optical element 186, 188, 190, 192, 194 with the optical waveguide core will relax manufacturing tolerances associated with mounting the optical waveguide 112 and allow use of optical waveguides having more variation in the core location. In particular, individual alignment of each optical channel through the optical block 118 may enable use of single mode optical fiber as the optical waveguide 112. Efficient optical coupling into single mode optical fiber has significantly tighter alignment tolerances than multimode fiber, which has been used in many prior art optical interconnect modules

[0107] The optical block 118 may have one or more alignment marks or features 199. The alignment marks or features 199 may be fabricated by a bulk manufacturing process or may be individually defined based at least in part on the location of the optical waveguides 112. The alignment marks or features 199 may be on the bottom surface of the optical block 118 (see FIG. 15). An example of such alignment features is described in Patent Cooperation Treaty Application No. PCT / US2024 / 030998 having the same assignee as the present disclosure, which is incorporated herein by reference in its entirety. The alignment marks or features 199 are arranged to assist in registration of the optical block subassembly 198 to the optical engine 108. For example, the alignment features or marks 199 on the optical block 118 depicted in FIG. 15 may be arranged to register with the alignment features 164 on the transparent substrate 116 depicted in FIGS. 12 and 13. For example, the alignment features or marks 199 on the optical block 118 depicted in FIG. 15 may be arranged to align with the alignment features 164 on the transparent carrier 116 depicted in FIGS. 12 and 13. Depending on the nature of the alignment features 164 and 199, the alignment features may register directly with each other (i.e. physically contact) or the alignment features 164 and 199 may indirectly register with each other, such as through anoptical block guide 230 (see FIG. 16). The registration may be an active registration using optical alignment of the alignment features or marks 199 with the alignment features 164, or a mechanical interference between the alignment features or marks 199 and the alignment features 164 that passively registers the optical block subassembly 198 to the optical engine 108. The placement of the optical element 186, 188, 190, 192, 194 within or on a surface of the optical block 118, may be determined at least in part by the location of the alignment features or marks 199 in addition to the location of each of the optical waveguides 112. In some embodiments, the alignment features or marks 199 may be made using the same processing tool used to define the optical element 186, 188, 190, 192, 194 within or on a surface of the optical block 118.

[0108] In another embodiment, rather than the optical block 118 having a pigtailed optical waveguide 112, the side surface 166 may be arranged to mate with a detachable optical waveguide, such as a plurality of optical fibers mounted in an optical ferrule. The optical ferrule may be a MT ferrule, but other types of optical ferrules may be used. The optical fibers may be arranged in a row extended in the lateral direction. There may be a single row of optical fibers or a plurality of rows of optical fibers. The side surface 166 may have one or more alignment features (not shown in FIG. 15) arranged to mate with corresponding alignment features on the detachable optical waveguide. An example of such alignment features is described in Patent Cooperation Treaty Application No PCT / US2024 / 030998 having the same assignee as the present disclosure, which is incorporated herein by reference in its entirety.

[0109] In other words, an optical block subassembly may be comprised of an optical block having a bottom surface and a side surface configured to transmit an optical beam and an alignment feature on the side surface configured to mate with an attachable / detachable optical fiber cable. The optical block includes a plurality of optical elements and each of the plurality of optical elements is configured to be associated with a corresponding optical waveguide of the attachable / detachable optical fiber cable and a location of each of the plurality of optical elements is individually defined at least in part by a position of the alignment features.

[0110] It should be appreciated that the optical block 118 may have a plurality of optical elements in any given optical channel. Some of the optical elements may be predefined by somebulk manufacturing process, such as molding, and some optical elements may be defined individually to optimize optical coupling into and out of the optical waveguide 112.

[0111] The reflective surface on the optical block may be formed through various methods. In some embodiments, the reflective surface may be a simple flat mirror. In other embodiments, the reflective surface may incorporate curved regions to provide additional optical power. The curved regions may be formed during initial manufacturing of the optical block or may be individually defined for each channel using additive manufacturing or other processing techniques. When individually defined, each curved region can be optimized for its specific channel, taking into account the position of the optical waveguide core.

[0112] FIG. 16 illustrates an optical coupling assembly 240 including an optical block guide 230 according to an embodiment of the present disclosure. The optical coupling assembly 240 may be comprised of an optical block subassembly 198, similar to that previously shown in FIG. 15, and an optical engine 108, similar to that previously shown in FIG. 13. The optical block subassembly 198 may have a surface optical element 188 on the bottom surface of the optical block 118. Also, on the bottom surface of the optical block 188 may be alignment features 199. An encapsulant 236 may fill a region between the optical waveguide 112 and the side surface of the optical block 118. Both the surface optical element 188 and alignment features 199 may be individually defined based on a position of the waveguide 112. In some alternative embodiments, both these elements may be made in a bulk manufacturing process or the alignment features 199 may be made using a bulk manufacturing process and the surface optical element 188 may be individually defined. The optical engine 108 may have an E / O component 125 which emits or receives an optical beam 104. The optical engine 108 may have a surface optical element 163 on a top surface of the transparent substrate 116. Also, on the top surface of the transparent substrate 116 may be alignment features 164. Both the surface optical element 163 and alignment features 164 may be individually defined based on a position of an active area (not visible in FIG. 16) of the E / O component 125. In some alternative embodiments, both these elements may be made in a bulk manufacturing process, or the alignment features 164 may be made using a bulk manufacturing process and the surface optical element 163 may be individually defined.

[0113] The optical block guide 230 may be formed from a transparent material, such as, but not limited to, glass. The optical block guide 230 may have top alignment features 232 formed in its top surface and bottom alignment features 234 formed in its bottom surface. The top alignment features 232 are configured to mate with alignment features 199 of the optical block subassembly 198 and the bottom alignment features are configured to mate with the alignment features 164 of the optical engine 108. The top and bottom alignment features 232 and 234 may be a slot in the optical block guide 230. Although not shown in FIG. 17, in some embodiments the top and bottom alignment features 232 and 234 may comprise a single feature, such as a through slot, that extends from the top to the bottom surface of the optical block guide 230. The top and bottom alignment features 232 and 234 may be made using a laser selective etching process in which regions of the optical block guide 230 are selectively irradiated and subsequently etched to remove material from the irradiated region.

[0114] An advantage of using the optical block guide 230 between the optical block subassembly 198 and the optical engine 108 is that the optical block alignment features 199 and the carrier subassembly alignment features 164 may both protrude from the surround surface. As such, both the optical block alignment features 199 and the optical engine alignment features 164 may be additively manufactured. In alternative embodiments, one or both the optical block alignment features 199 and the optical engine alignment features 164 may be fabricated using a bulk manufacturing process.

[0115] FIG. 17 illustrates an exemplary method 400 of assembling an optical block subassembly according to an embodiment of the present disclosure. In a first step 402 a plurality of bulk features may be fabricated into an optical block by a bulk manufacturing process, such as but not limited to molding or photolithography. The plurality of features may include a plurality of alignment grooves or holes which support and register a plurality of optical waveguides. The plurality of bulk features may also include a refractive lens on either a bottom or side surface or a curved mirror on a reflective surface of the optical block. The plurality of bulk features may further include alignment marks and features that assist in alignment of the optical block to an optical engine. In a second step 404, a plurality of optical waveguides may be permanently affixed to a waveguide mounting portion of the optical block. The plurality of optical waveguides may be partof a ribbon cable and may be affixed to the optical block simultaneously in a single processing step. The optical block may have a plurality of alignment features that help to accurately register the position of the optical waveguides relative to other features on the optical block. The plurality of alignment features may be a regularly spaced pattern of grooves, which help align each optical waveguide. The plurality of optical waveguides may be a plurality of optical fibers. The plurality of optical fibers may be dispersed in a row having a common pitch between adjacent optical fibers. In a third step 406, a processing head is aligned based on a position of the optical waveguide 112. The alignment of the processing head may also be based at least in part on the location of the alignment marks or features 199 (see FIGS. 15 and 16). In a fourth step 408, an optical element may be defined within or on a surface of the optical block. A location of the optical element may be based, at least in part, on a position of the optical waveguide 112 and optionally the alignment marks and features 199. In some embodiments, the location of the optical element may be based on a position of a core of the optical waveguide. In some embodiments, the optical element may be a plurality of optical elements serially arranged within or on a surface of the optical block. The location of the optical element may be chosen to optimize optical coupling into and / or out of the optical waveguide. The optical element may be an additively manufactured feature on the side surface 166, bottom surface 168 or reflective surface 114. Alternatively, the optical element may be defined within the bulk of the optical block by a spatially localized change in the refractive index, for instance, by scanning a focal spot of a processing optical beam emitted by a laser processing tool. It should be noted that some laser processing techniques, particularly those that use two-photon polymerization as mentioned above, serve as both laser processing and additive manufacturing methods simultaneously, as they selectively build up material using focused laser energy. In a fifth step 410, a decision is made whether an optical element(s) has been written for all optical waveguides that are affixed to the optical block. If not, the method returns to step 406 where the processing head is aligned with another optical waveguide and the defining step 408 is repeated. If the decision in step 410 is a yes, indicating that all optical waveguides have had corresponding optical elements defined, the method 400 proceeds to step 412 which may represent a completed optical block subassembly. The optical block subassembly may then be integrated with an optical engine and further integrated into an optical interconnect module as described above.

[0116] A plurality of optical blocks may be fabricated on a single planar wafer. Individual optical blocks may be singulated from the wafer. The optical waveguides may be affixed to the optical blocks either before or after singulation. In an embodiment, the optical waveguides may be a ribbon optical fiber cable and a plurality of ribbon optical fiber cables may be affixed to a row of cojoined optical blocks prior to the singulation step. Since the optical waveguides are permanently affixed to the optical block after this step, defining of the optical elements may occur while the optical blocks remain cojoined.

[0117] The manufacturing process may proceed in different sequences depending on the specific implementation requirements. In one approach, the electrooptic components are mounted first, followed by writing of the optical elements in the transparent substrate. In another approach, the optical elements are written first, and then the electrooptic components are precisely mounted in alignment with the pre-written optical elements. Similarly, for the optical block, the optical waveguides may be mounted before or after defining optical elements in or on the optical block. The sequence choice may depend on various factors including the specific materials used, the type of optical elements being formed, and the available manufacturing equipment. In all cases, the ability to individually optimize each optical channel provides flexibility in the manufacturing process while maintaining high coupling efficiency.

[0118] FIG. 18 shows an exemplary optical block subassembly 198 that may result from application of the assembly method 400 depicted in FIG. 17. A plurality of optical waveguides 112 are affixed to an optical block 118. The plurality of optical waveguides 112 may be part of an optical fiber cable 102. In this example, there are twelve optical waveguides 112 in the optical fiber cable 102, which is a ribbon cable. Each optical waveguide 112 has an associated curved mirror 191 on the reflective surface 114. Each curved mirror 191 may be defined after its associated optical waveguide 112 has been affixed to the optical block 118. The location and curvature of the curved mirror 191 may be individually optimized to facilitate efficient optical coupling into or out of each of the optical waveguides 112.

[0119] In yet another embodiment, an optical block subassembly 198 may be mated with an optical engine 108 prior to definition of an optical element that will enable efficient opticalcoupling between the E / O components 125 in the optical engine 108 and the optical waveguides 112 in the optical block subassembly 198. The optical element can be defined anywhere along the optical path between the E / O components 125 and the optical waveguides 112 In particular, the optical element may be a curved mirror 191 defined on the reflective surface 114 of the optical block 118.

[0120] While FIGS. 15 and 17 have depicted the optical block 118 as a monolithic structure, an alternative embodiment, the optical block 118 may be a unitary structure composed of different materials permanently bonded to each other. The materials may be selected based on their material properties. In a manner analogous to that depicted in FIG. 11, the optical block 118 may be a unitary structure comprising individual elements bonded together, with at least one individual element having desirable properties for defining an optical element and the other individual elements having desirable mechanical properties. FIGS. 19 and 20 show different embodiments of such a composite optical block subassembly 193. The composite optical block subassembly 193 includes a composite optical block 197 formed from bonding together two transparent elements. A first transparent element 185 having desirable mechanical properties and a second transparent element 195 having desirable properties for defining an optical element. The second transparent element 195 may take the form of a rectangular parallel opiped as shown in FIG. 19. Two optical elements may be defined within the second transparent element 195, a first optical element may be a beam steering diffractive optical element 175 that serves to redirect the optical axis 105 in a manner similar to that of reflective surface shown in FIG. 15. The second optical element 177 may be formed along the optical axis 105 in a region between the side surface 166 and the beam steering diffractive optical element 175. The second optical element 177 may be a diffractive or refractive optical element configured to collimate an optical beam exiting the optical waveguide 112 (Rx channel) or focusing an optical beam into the optical waveguide 112 (Tx channel).

[0121] FIG. 20 shows a different embodiment of a composite optical block 197. In this embodiment, there are three different elements bonded together to form the composite optical block 197. A first transparent element 185 having desirable mechanical properties, a second transparent element 195 having desirable properties for defining an optical element and a thirdtransparent element 174. The third transparent element 174 includes the reflective surface 114 and redirects the optical axis 105. The third transparent element 174 may have a simple triangular cross-sectional shape as shown in FIG. 19, making this element easy to fabricate. The second transparent element 195 may again take the form of a rectangular parallelepiped; however, unlike the second transparent element 195 depicted in FIG. 19, the second transparent element 195 in FIG. 20 has only the second optical element 177 defined within it.

[0122] While FIGS. 19 and 20 depict two specific arrangements of a composite optical block 197, it should be appreciated that a composite optical block can be composed of different shapes and arrangements of transparent elements other than those depicted in FIGS. 19 and 20. In this disclosure the term optical block may refer to both a monolithic optical block formed from a single material or a composite optical block formed from a plurality of elements.

[0123] FIG. 21 depicts an embodiment of an optical engine 108 in which an individually defined optical element 109 is defined on a top surface 153 of an encapsulant 151. Although not shown in FIG. 21 the individually defined optical element 109 may alternatively be defined within the encapsulant 151. Alignment features (not shown in FIG. 21) may also be situated on the top surface 153 or within the encapsulant 151 An advantage of this embodiment is that the transparent substrate 115 may be omitted. In some cases, a surface profile of the encapsulant may form the optical element 109. Alternatively, when defined within the encapsulant 151, the individually defined optical element 109 may be formed by inducing a spatially localized change in the refractive index of the encapsulant material, similar to the methods used for forming internal elements within a transparent substrate.

[0124] In summary, the invention disclosed herein describes a system and method that establishes an optical path by defining an optical element along that path that changes the wavefront curvature of an optical beam propagating along the optical path. The invention may be applied to an optical interconnect module having a plurality of transmit and / or receive channels. The optical path in each channel is individually defined for that channel so that an E / O component and optical waveguide are optically aligned and can efficiently propagate an optical signal between them. The optical element may be defined on a surface that intersects the optical path or within atransparent material through which the optical path propagates. Specifically, the optical element may be defined on or in a transparent substrate and / or optical block. The transparent substrate and optical block may each be formed as either monolithic or composite structures. For composite structures, different materials may be selected based on their specific properties. For example, one material may be chosen for superior mechanical properties such as thermal stability and structural rigidity, while another material may be optimized for optical properties such as the ability to form internal optical elements through laser processing. In one embodiment, a material comprising a silica scaffolding with polymer-filled voids may be used for regions where optical elements are to be written, as this structure allows significant localized changes in refractive index through laser processing. In another embodiment, the optical element may be defined through an additive manufacturing process. Alignment features may be defined during the same process step that defines the optical element. The E / O components and associated electronics, such as a laser driver and TIA, may use wirebond electrical connections. In some embodiments, some of the components may use wirebond electrical connections and some may use a flip-chip electrical connection.

[0125] It should be noted that the illustrations and discussions of the embodiments and examples shown in the figures are for exemplary purposes only and should not be construed limiting the disclosure. One skilled in the art will appreciate that the present disclosure contemplates a range of possible modifications of the various aspects, embodiments and examples described herein. For example, some fiducial mark other than a contact ring may be used to align an optical element with an active area of an E / O component. Not all optical channels in an optical interconnect module may need to have an individually defined optical element. In particular, the transmit channels may have an individually defined optical element, but no individually defined optical element may be present in a receive channel.

[0126] While the foregoing description primarily details arrangements using wirebonded electrooptic components (e.g. 125) mounted such that the active area (e.g. 134) faces away from the heat sink (e.g. 116), with the optical signal path originating from or terminating at this upward- facing active area (e.g., passing through encapsulant 151 and potentially a transparent substrate 115), the general principles of utilizing individually defined optical elements are not limited to thisspecific configuration or mounting orientation. In alternative embodiments, the electrooptic component itself may be configured differently, for example, for signal transmission through its own substrate material, irrespective of whether wirebond or other electrical connections are used. For instance, a Vertical Cavity Surface Emitting Laser (VCSEL) may be constructed as a "back- emitting" VCSEL, where the optical signal exits through the VCSEL's substrate (i.e., the side typically mounted towards a support like the heat sink 116 in the main embodiments). Similarly, a photodetector may be configured as a "back-receiving" photodetector, where the optical signal enters through the photodetector's substrate to reach the active area (134). In such configurations, the substrate material of the electrooptic component (e.g., GaAs, InP, Si) is substantially transparent at the operating wavelength of the optical signal. Even in these alternative electrooptic component configurations where the primary light path is through the component's own substrate, individually defined optical elements (e g , 106, 163, 186, 188, 190, 191, or elements defined on / in encapsulant 151 as in FIG. 21) situated in the optical path (potentially within or on an overlying transparent substrate 115, an optical block 118, or an encapsulant 151) can still be employed. These elements would be individually defined and aligned relative to the active area (134) to facilitate efficient optical coupling, specifically accounting for the optical path that passes through the electrooptic component's substrate. The alignment and definition processes (e.g., method 200, 400) can be adapted to define elements aligned via this alternative path.

[0127] It should be understood that the concepts described above with the above-described embodiments and examples may be employed alone or in combination with any of the other embodiments and examples described above. It should further be appreciated that the various alternatives described above with respect to one illustrated embodiment can apply to all other embodiments and examples described herein, unless otherwise indicated. Reference is therefore made to the claims.

Claims

CLAIMS1. An optical engine comprising: a heat sink having a first major surface and an opposed second major surface; an electrooptic component having an active area, wherein the electrooptic component is mounted to the first major surface and the active area faces away from the first major surface; and an individually defined optical element situated in an optical path that originates from or terminates in the active area, wherein the individually defined optical element is optically aligned with the active area of the electrooptic component.

2. The optical engine of claim 1, wherein the individually defined optical element has a spatially varying index of refraction.

3. The optical engine of any one of claims 1-2, wherein the individually defined optical element is an internal diffractive optical element situated within a transparent substrate positioned in the optical path.

4. The optical engine of any one of claims 1-2, wherein the individually defined optical element is an internal refractive optical element situated within a transparent substrate positioned in the optical path.

5. The optical engine of any one of claims 1-2, wherein the individually defined optical element is combination of an internal refractive optical element and an internal diffractive optical element situated within a transparent substrate positioned in the optical path.

6. The optical engine of any one of claims 1-5, wherein the individually defined optical element is in a transmit channel and is configured to reduce divergence of an optical beam emitted by the active area of the electrooptic component.

7. The optical engine of claim 6, wherein the individually defined optical element is configured to collimate the optical beam.

8. The optical engine of any one of claims 6-7, wherein the individually defined optical element is configured to orient an optical axis of the optical beam perpendicular to a top surface of a transparent substrate positioned in the optical path within a manufacturing tolerance.

9. The optical engine of any one of claims 1-5, wherein the individually defined optical element is in a receive channel and is configured to focus an optical beam incident on a top surface of a transparent substrate positioned in the optical path on to the active area of the electrooptic component.

10. The optical engine of any one of claims 1-3 and 5-9, wherein the individually defined optical element comprises a Fresnel zone plate11. The optical engine of any one of claims 1-3 and 6-10, wherein the individually defined optical element comprises a plurality of individually defined optical elements arranged in series within a transparent substrate positioned in the optical path.

12. The optical engine of any one of claims 1-11, further comprising a refractive lens on a top surface of a transparent substrate positioned in the optical path.

13. The optical engine of any one of claims 1-12, wherein the individually defined optical element is configured to pick-off a portion of an optical beam transmitted through the individually defined optical element.

14. The optical engine of any one of claims 1-12, wherein the electrooptic component is a plurality of electrooptic components.

15. The optical engine of claim 14, wherein the plurality of electrooptic components comprises two lasers and two photodetector die.

16. The optical engine of claim 14, wherein the plurality of electrooptic components comprises a photonic integrated circuit and a photodetector die.

17. The optical engine of claim 14, wherein each electrooptic component of the plurality of electrooptic components has a corresponding individually defined optical element that is individually aligned with that electrooptic component independent of alignment of other individually defined optical elements.

18. The optical engine of any one of claims 1-13, wherein the electrooptic component is a single photonic integrated circuit.

19. The optical engine of any one of claims 1-18, wherein a refractive index profile of the individually defined optical element varies in three dimensions.

20. The optical engine of any one of claims 1-19, wherein a refractive index profile of the individually defined optical element is determined using artificial intelligence.

21. The optical engine of any one of claims 1-20, further including a transparent substrate positioned in the optical path, wherein the transparent substrate comprises a plurality of transparent layers bonded together to form a unitary structure.

22. The optical engine of claim 21, wherein the plurality of transparent layers comprises a first transparent layer and a second transparent layer, the first transparent layer forming a bottom surface of the transparent substrate and the second transparent layer forming a top surface of the transparent substrate.

23. The optical engine of claim 22, wherein the individually defined optical element is located within the second transparent layer.

24. The optical engine of any one of claims 22-23, wherein the first transparent layer has superior mechanical properties compared to the second transparent layer.

25. The optical engine of any one of claims 1-24, wherein an alignment mark is situated on or directly beneath a top surface of a transparent substrate positioned in the optical path.

26. The optical engine of claim 25, wherein the alignment mark is written during the same processing step as the individually defined optical element.

27. An optical coupling assembly comprising: a heat sink having a first major surface and an opposed second major surface; an electrooptic component having an active area mounted to the first major surface, wherein the active area faces away from the first major surface; a transparent substrate including an individually defined optical element within or on a surface of the transparent substrate, wherein the individually defined optical element is optically aligned with the active area of the electrooptic component; an optical block aligned with the transparent substrate; and an optical waveguide supported by the optical block in optical communication with the active area.

28. The optical coupling assembly of claim 27, wherein an optical beam propagates through the optical block between the active area and the optical waveguide.

29. The optical coupling assembly of any one of claims 27-28, wherein the optical waveguide is mounted to the optical block.

30. The optical coupling assembly of any one of claims 27-29, further comprising a refractive lens situated on a face of the optical block.

31. The optical coupling assembly of any one of claims 27-30, wherein the optical waveguide is an optical fiber.

32. The optical coupling assembly of any one of claims 27-31, wherein the optical beam is collimated in a region between the transparent substrate and the optical block.

33. The optical coupling assembly of any one of claims 27-32, further comprising a reflective surface situated on a face of the optical block.

34. The optical coupling assembly of any one of claims 27-33, wherein the individually defined optical element picks-off a portion of the optical beam transmitted through the individually defined optical element.

35. The optical coupling assembly of any one of claims 27-34, further comprising a plurality of alignment marks situated on or directly beneath a top surface of the transparent substrate that aid in positioning the optical block on the transparent substrate.

36. The optical coupling assembly of any one of claims 27-35, wherein the individually defined optical element is an internal diffractive optical element within the transparent substrate.

37. The optical coupling assembly of any one of claims 27-35, wherein the individually defined optical element is an internal refractive optical element within the transparent substrate.

38. The optical coupling assembly of any one of claims 27-35, wherein the individually defined optical element is a combination of an internal diffractive optical element and an internal refractive optical element within the transparent substrate.

39. The optical coupling assembly of any one of claims 27-38, wherein the transparent substrate comprises a plurality of transparent layers bonded together to form a unitary structure.

40. The optical coupling assembly of claim 39, wherein the plurality of transparent layers comprises a first transparent layer and a second transparent layer, the first transparent layer forming the bottom surface of the transparent substrate and the second transparent layer forming the top surface of the transparent substrate.

41. The optical coupling assembly of claim 40, wherein the individually defined optical element is located within the second transparent layer.

42. The optical coupling assembly of any one of claims 40-41, wherein the first transparent layer has superior mechanical properties compared to the second transparent layer.

43. The optical coupling assembly of any one of claims 27-42, wherein an alignment mark is situated on or directly beneath a top surface of the transparent substrate and helps to position the optical block on the top surface of the transparent substrate.

44. The optical coupling assembly of claim 43, wherein the alignment mark is written during the same processing step as the individually defined optical element.

45. An optical interconnect module comprising: an electrooptic component including an active area configured to emit or receive an optical signal; and an individually defined optical element in optical alignment with the active area.

46. The optical interconnect module of claim 45, wherein the electrooptic component includes a plurality of active areas and further comprises a plurality of individually defined optical elements, wherein each of the plurality of active areas is in optical alignment with an associated individually defined optical element of the plurality of optical elements.

47. The optical interconnect module of claim 45 or 46, wherein the electrooptic component comprises a plurality of electrooptic components.

48. The optical interconnect module of claim 45, wherein the electrooptic component mounted is mounted to a heat sink and arranged to emit an optical beam through a transparent substrate positioned above the electrooptic component or detect an optical beam transmitted through the transparent substrate.

49. The optical interconnect module of any one of claims 45-48, wherein the individually defined optical element comprises two individually defined optical elements arranged in series within a transparent substrate positioned in the optical path.

50. The optical interconnect module of any one of claims 45-49, further comprising a transparent substrate and a refractive lens formed on the transparent substrate.

51. The optical interconnect module of any one of claims 45-50, wherein the individually defined optical element picks-off a portion of an optical beam transmitted through the individually defined optical element.

52. The optical interconnect module of claim 51, wherein the picked-off portion of the optical beam is sampled by a monitor photodiode.

53. The optical interconnect module as recited in any one of claims 45-52, wherein the optical interconnect module has a plurality of transmit channels.

54. The optical interconnect module of claim 53, wherein each transmit channel of the plurality of transmit channels includes an individually defined optical element that is individually aligned with its corresponding electrooptic component independent of the alignment of individually defined optical elements in other transmit channels.

55. The optical interconnect module of any one of claims 45-54, wherein the optical interconnect module has a plurality of receive channels.

56. The optical interconnect module of claim 55, wherein each receive channel of the plurality of receive channels includes an individually defined optical element that is individually aligned with its corresponding electrooptic component independent of the alignment of individually defined optical elements in other receive channels.

57. The optical interconnect module of any one of claims 46-56, wherein the electrooptic component is a plurality of electrooptic components.

58. The optical interconnect module of claim 57, wherein the plurality of electrooptic components comprises two laser die and two photodetector die.

59. The optical interconnect module of claim 57, wherein the plurality of electrooptic components comprises a photonic integrated circuit and a photodetector die60. The optical interconnect module of any one of claims 45-56, wherein the electrooptic component is a single photonic integrated circuit.

61. The optical interconnect module of any one of claims 45-60, wherein a refractive index profile of the individually defined optical element is determined using artificial intelligence.

62. The optical interconnect module of any one of claims 45-61, wherein the individually defined optical element is an internal diffractive optical element within a transparent substrate positioned in the optical path.

63. The optical interconnect module of claim 62, wherein the internal diffractive optical element comprises a Fresnel zone plate.

64. The optical interconnect module of any one of claims 45-61, wherein the individually defined optical element is an internal refractive optical element within a transparent substrate positioned in the optical path.

65. The optical interconnect module of any one of claims 45-61, wherein the individually defined optical element is a combination of an internal diffractive optical element and an internal refractive optical element within a transparent substrate positioned in the optical path.

66. The optical interconnect module of any one of claims 45-65, further comprising a transparent substrate positioned in the optical path, wherein the transparent substrate comprises a plurality of transparent layers bonded together to form a unitary structure.

67. The optical interconnect module of claim 66, wherein the plurality of transparent layers comprises a first transparent layer and a second transparent layer.

68. The optical interconnect module of claim 67, wherein the individually defined optical element is located within the second transparent layer.

69. The optical interconnect module of any one of claims 67-68, wherein the first transparent layer has superior mechanical properties compared to the second transparent layer.

70. The optical interconnect module of any one of claims 45-69, further comprising a heat sink having a first major surface and a second major surface, wherein an alignment mark is situated on or directly beneath a top surface of a transparent substrate positioned above the heat sink and helps to position an optical block on the top surface of the transparent substrate.

71. The optical interconnect module of claim 70, wherein the alignment mark is written during the same processing step as the individually defined optical element.

72. A method of assembling an optical engine comprising: mounting an electrooptic component on a first major surface of a heat sink, wherein the electrooptic component has an active area facing away from the first major surface which is configured to emit or detect an optical beam; aligning a processing head of a laser processing tool with the active area; and defining an individual optical element in optical alignment with the active area of the electrooptic component.

73. The method of claim 72, wherein the electrooptic component includes a plurality of active areas and an individually defined optical element is defined in optical alignment with each of the plurality of active areas.

74. The method of claim 72 or 73, wherein the electrooptic component comprises a plurality of electrooptic components.

75. The method of claim 72, wherein the active area of the electrooptic component is a plurality of active areas.

76. The method of claim 73, wherein each of the plurality of active areas has a corresponding individual optical element defined therein.

77. The method of any one of claims 74-76, wherein the electrooptic component is a plurality of electrooptic components.

78. The method of claim 77, wherein all active areas in each of the plurality of electrooptic component have a corresponding individual optical element defined therein.

79. The method of any one of claims 72-78, wherein the active area is energized during alignment of the processing head.

80. The method of any one of claims 72-78, wherein the active area is not energized during the alignment of the processing head.

81. The method of claim 80, wherein the processing head is aligned with a contact ring that surrounds or substantially surrounds the active area.

82. The method of any one of claims 73-81, wherein each active area of the plurality of active areas has its corresponding individual optical element individually written within or on atransparent substrate positioned above the electrooptic component, so that each individual optical element is in optical alignment with its corresponding active area.

83. The method of any one of claims 72-82, wherein the electrooptic component is a laser and the active area of the laser is configured to emit an optical beam that is collimated by the individual optical element.

84. The method of any one of claims 72-82, wherein the electrooptic component is a photodetector and an optical beam received by the active area of the photodetector is focused by the individual optical element.

85. The method of any one of claims 72-84, wherein the defining of the individual optical element is achieved by scanning a focal spot of a processing optical beam emitted by the laser processing tool.

86. The method of any one of claims 72-85, wherein the individual optical element is an individual diffractive optical element defined within or on a transparent substrate positioned above the electrooptic component.

87. The method of claim 86, wherein the individual diffractive optical element comprises a Fresnel zone plate.

88. The method of any one of claims 72-85, wherein the individual optical element is an individual refractive optical element defined within or on a transparent substrate positioned above the electrooptic component.

89. The method of any one of claims 72-85, wherein the individual optical element is a combination of an individual diffractive optical element and an individual refractive optical element defined within or on a transparent substrate positioned above the electrooptic component.

90. The method of any one of claims 72-89, further comprising providing a transparent substrate positioned above the electrooptic component, wherein the transparent substrate comprises a plurality of transparent layers bonded together to form a unitary structure.

91. The method of claim 90, wherein the plurality of transparent layers comprises a first transparent layer and a second transparent layer, the first transparent layer forming the bottom surface of the transparent substrate and the second transparent layer forming the top surface of the transparent substrate.

92. The method of claim 91, wherein the individual optical element is located within the second transparent layer.

93. The method of any one of claims 91-92, wherein the first transparent layer has superior mechanical properties compared to the second transparent layer.

94. The method of any one of claims 72-93, further comprising defining an alignment mark on a top surface of a transparent substrate positioned above the electrooptic component to help position an optical block.

95. The method of claim 94, wherein the alignment mark is written by the laser processing tool during the same processing step as the individual optical element.

96. A method of assembling an optical engine comprising: mounting an electrooptic component having a plurality of active areas on a first major surface of a heat sink, wherein each active area of the plurality of active areas faces away from the first major surface and is configured to emit or detect a corresponding optical beam; aligning a processing head of a processing tool with a first active area of the plurality of active areas; defining a first individual optical element using the processing tool, wherein the first individual optical element is in optical alignment with the first active area of the electrooptic component; andrepeating the aligning and defining steps for each active area of the plurality of active areas.

97. The method of claim 96, wherein the electrooptic component is a laser and each active area of the plurality of active areas is configured to emit a corresponding optical beam.

98. The method of claim 97, wherein each of the emitted corresponding optical beams is collimated by its corresponding first individual optical element.

99. The method of any one of claims 97-98, wherein each of the emitted corresponding optical beams has an optical axis and each optical axis is oriented to be perpendicular to a top surface of a transparent substrate positioned above the electrooptic component within a manufacturing tolerance.

100. The method of any one of claims 96-99, wherein the first individual optical element is an individual diffractive optical element defined within or on a transparent substrate positioned above the electrooptic component.

101. The method of claim 100, wherein the individual diffractive optical element comprises a Fresnel zone plate.

102. The method of any one of claims 96-99, wherein the first individual optical element is an individual refractive optical element defined within or on a transparent substrate positioned above the electrooptic component.

103. The method of any one of claims 96-99, wherein the first individual optical element is a combination of an individual diffractive optical element and an individual refractive optical element defined within or on a transparent substrate positioned above the electrooptic component.

104. The method of any one of claims 96-103, further comprising providing a transparent substrate positioned above the electrooptic component, wherein the transparent substrate comprises a plurality of transparent layers bonded together to form a unitary structure.

105. The method of claim 104, wherein the plurality of transparent layers comprises a first transparent layer and a second transparent layer, the first transparent layer forming the bottom surface of the transparent substrate and the second transparent layer forming top surface of the transparent substrate.

106. The method of claim 105, wherein the first individual optical element is located and defined within the second transparent layer.

107. The method of any one of claims 105-106, wherein first transparent layer has superior mechanical properties compared to the second transparent layer.

108. The method of any one of claims 96-107, further comprising providing an alignment mark on a top surface of a transparent substrate positioned above the electrooptic component to help position an optical block.

109. The method of claim 108, wherein the alignment mark is written by the processing tool during the same processing step as the first individual optical element.

110. An optical engine comprising: a heat sink having a first major surface; an electrooptic component having an active area and wirebond pads, wherein the electrooptic component is mounted to the first major surface of the heat sink and the active area faces away from the first major surface; wirebonds electrically connected to the wirebond pads; an encapsulant covering at least a portion of the electrooptic component and the wirebonds; a transparent substrate positioned above the electrooptic component such that an optical path between the active area and a location above the transparent substrate passes through the encapsulant and the transparent substrate; and an individually defined optical element situated within the transparent substrate and optically aligned with the active area.

111. The optical engine of claim 110, wherein the electrooptic component thas a plurality of active areas and further comprises a plurality of individually defined optical elements, wherein each individually defined optical element is individually defined based at least in part on a position of a corresponding active area.

112. A method of assembling an optical engine comprising: mounting an electrooptic component to top surface of a heat sink, wherein the electrooptic has an active area that faces away from the heat sink; making a wirebond electrical connection to the electrooptic component; encapsulating the wirebonds; mounting the transparent substrate above the wirebonds; aligning a processing head of a processing tool with the active area; and defining an individual optical element using the processing tool, wherein the individual optical element is in optical alignment with the active area of the electrooptic component.

113. An optical block subassembly comprising: an optical block, wherein the optical block has a bottom surface and a side surface configured to transmit an optical beam, a plurality of optical waveguides affixed to the optical block; and a plurality of optical elements, wherein each of the plurality of optical elements is associated with a corresponding optical waveguide and a location of each of the plurality of optical elements is individually defined at least in part by a position of each of the optical waveguides.

114. The optical block subassembly as recited in claim 113, wherein a position of each optical waveguide is determined by a processing tool and a location of the associated optical element is defined by a position of a processing head of the processing tool.

115. The optical block subassembly as recited in claim 113 or 114, wherein each optical element is defined on a surface of the optical block by additive manufacturing.

116. The optical block subassembly as recited in claim 115, wherein the surface is the bottom surface or the side surface and the optical element is a refractive lens.

117. The optical block subassembly as recited in claim 115, wherein the surface is a reflective surface configured to redirect the optical beam and the optical element is a curved mirror.

118. The optical block subassembly as recited in claim 113 or 114, wherein each optical element is defined by inducing a spatially localized refractive index change within the optical block.

119. The optical block subassembly as recited in any one of claims 113 to 118, wherein the plurality of optical waveguides is a plurality of optical fibers arranged as an optical fiber ribbon cable.

120. The optical block subassembly as recited in any one of claims 113 to 119, wherein the location of each of the plurality of optical elements is individually defined at least in part by a position of an alignment mark or feature on the optical block.

121. The optical block subassembly as recited in claim 120, wherein the position of the alignment mark or feature is determined by the processing tool.

122. A method of assembling an optical block subassembly comprising: affixing a plurality of optical waveguides on an optical block; aligning a processing head of a processing tool with a first optical waveguide of the plurality of optical waveguides; defining a first optical element within or on a surface of the optical block using the processing tool, wherein the first optical element is in optical alignment with the first optical waveguide; and repeating the aligning and defining steps for each optical waveguide of the plurality of optical waveguides.

123. The method of claim 122, wherein the defining of the first optical element is achieved by scanning a focal spot of a processing optical beam emitted by a laser processing tool.

124. The method of claim 122, wherein the defining of the first optical element is achieved by forming a curved mirror on a reflective surface of the optical block by an additive manufacturing process.

125. The method of claim 122, wherein the defining of the first optical element is achieved by forming a refractive lens on a bottom or side surface of the optical block by an additive manufacturing process.

126. An optical interconnect module comprising: an optical engine, wherein the optical engine comprises an electrooptic component and a transparent substrate; an optical block subassembly, wherein an optical waveguide is affixed to the optical block subassembly; and an individually defined optical element, wherein the optical element is configured to help optically couple an optical beam between the electrooptic element and the optical waveguide and the individually defined optical element is defined based at least in part on a position of the electrooptic element or the optical waveguide.

127. The optical interconnect module as recited in claim 126, wherein the individually defined optical element is located on a surface of or within the transparent substrate.

128. The optical interconnect module as recited in claim 126, wherein the individually defined optical element is located on a surface of or within the optical block of the optical block subassembly.

129. The optical interconnect module as recited in any one of claims 126 to 128, wherein the optical waveguide is a plurality of optical waveguides, the electrooptic element is a plurality of electrooptic elements, and the individually defined optical element is a plurality of individuallydefined optical elements, and each of the plurality of individually defined optical elements helps optically couple an associated electrooptic element of the plurality of electrooptic elements with an associated optical waveguide of the plurality of optical waveguides.

130. The optical interconnect module as recited in any one of claims 126 to 129, wherein additive manufacturing or laser processing is used to define the individually defined optical element.

131. The optical interconnect module as recited in any one of claims 126 to 130, further comprising an alignment feature on the optical engine and a mating alignment feature on the optical block subassembly, wherein mating the alignment feature and mating alignment feature places the electrooptic element and the optical waveguide in optical alignment.

132. The optical interconnect module as recited in claim 131, wherein either the alignment feature or the mating alignment feature is defined at least in part by an additive manufacturing process.

133. The optical interconnect module as recited in any one of claims 126 to 132, wherein each individually defined optical element is defined on a surface of the optical block or the transparent substrate by additive manufacturing.

134. The optical interconnect module as recited in claim 133, wherein the surface is a bottom surface or a side surface of the optical block and the individually defined optical element is a refractive lens.

135. The optical interconnect module as recited in claim 133, wherein the surface is a reflective surface on the optical block configured to redirect the optical beam and the individually defined optical element is a curved mirror.

136. The optical interconnect module as recited in claim 133, wherein the surface is a top surface of the transparent substrate and the individually defined optical element is a refractive lens.

137. The optical interconnect module as recited in any one of claims 126 to 132, wherein the individually defined optical element is defined by inducing a spatially localized refractive index change within the optical block or transparent substrate.

138. The optical interconnect module as recited in any one of claims 126 to 137, wherein the electrooptic element is a plurality of electrooptic elements each having an active area and the individually defined optical element is a plurality of individually defined optical elements, wherein each individually defined optical element of the plurality of individually defined optical elements is individually defined based at least in part on a position of a corresponding active area.

139. An optical coupling assembly comprising: a transparent substrate having a top surface and an opposed bottom major surface; an electrooptic component having an active area configured to emit an optical beam through the transparent substrate or detect an optical beam transmitted through the transparent substrate; an optical block positioned above on the top surface supporting an optical waveguide; a core of the optical waveguide in optical communication with the active area; and an individually defined optical element situated between the electrooptic component and the optical waveguide, wherein a location of the individually defined optical element is based at least in part on a position of the active area or the core of the optical waveguide.

140. The optical coupling assembly as recited in claim 139, wherein the optical waveguide is a plurality of optical waveguides, the electrooptic component is a plurality of electrooptic components each having an associated active area, and the individually defined optical element is a plurality of individually defined optical elements, wherein each of the plurality of individually defined optical elements helps optically couple an associated electrooptic component of the plurality of electrooptic components with an associated optical waveguide of the plurality of optical waveguides.

141. The optical coupling assembly as recited in claim 140, wherein additive manufacturing or laser processing is used to define each individually defined optical element of the plurality of individually defined optical elements.

142. An optical block subassembly comprising: an optical block, wherein the optical block has a bottom surface and a side surface configured to transmit an optical beam, an alignment feature on the side surface configured to mate with an attachable / detachable optical fiber cable; and a plurality of optical elements, wherein each of the plurality of optical elements is configured to be associated with a corresponding optical waveguide of the attachable / detachable optical fiber cable and a location of each of the plurality of optical elements is individually defined at least in part by a position of the alignment feature.

143. An optical coupling assembly comprising: a transparent substrate having a top surface and an opposed bottom surface; a plurality of electrooptic components positioned below the bottom, each electrooptic component having an active area; and a plurality of individually defined optical elements situated within or on the top or bottom surface of the transparent substrate, wherein each individually defined optical element is individually aligned with a corresponding active area of the plurality of electrooptic components, such that each individually defined optical element's position is customized based on the position of its corresponding active area independent of the positions of other individually defined optical elements.

144. A method of manufacturing an optical coupling assembly comprising: mounting a plurality of electrooptic components to a top surface of a heat sink, each electrooptic component having an active area facing away from the heat sink; for each active area of the plurality of electrooptic components: individually aligning a processing head of a laser processing tool with that active area; anddefining an internal optical element within a transparent substrate positioned above the electrooptic element at a position optimized for that specific active area independent of the positions of other internal optical elements, wherein the resulting plurality of optical elements are each individually customized for their corresponding active areas without compromise for alignment with other active areas.

145. An optical coupling assembly comprising: a transparent substrate having a top surface and an opposed bottom surface; a plurality of electrooptic components mounted to a top surface of a heat sink, each electrooptic component having multiple active areas facing towards the transparent substrate; an optical block positioned above the electrooptic components; a plurality of optical waveguides supported by the optical block; and a plurality of optical elements situated within, on the first surface or on the second surface the transparent substrate, wherein each optical element is individually written and aligned with respect to a corresponding active area after mounting of the electrooptic components and before mounting of the optical block, and the optical elements are configured to provide collimated optical beams in a region between the transparent substrate and optical block to accommodate lateral positioning tolerances between the transparent substrate and optical block while maintaining optical coupling efficiency.

146. A method of manufacturing an optical coupling assembly comprising: mounting a plurality of electrooptic components to a top surface of a heat sink, each electrooptic component having multiple active areas; for each active area: determining a position of the active area; aligning a laser processing tool with the determined position; writing a customized optical element within or on a surface of a transparent substrate positioned above the electrooptic component using a processing tool, wherein the customized optical element is configured to provide a collimated optical beam;writing an alignment feature on a surface of or within transparent substrate using the same processing tool while maintaining alignment with the active area; and mounting an optical block supporting optical waveguides above the transparent substrate using the alignment features to achieve registration between the optical block and transparent substrate.

147. An optical interconnect module comprising: an optical engine comprising an electrooptic element including a plurality of active; a wirebond electrical connection; an optical block subassembly comprising a plurality of optical waveguides, wherein each of the plurality of active areas is in optical alignment with an associated optical waveguide of the plurality of optical waveguides; and a plurality of individually defined optical elements, wherein each individually defined optical element of the plurality of optical elements is in optical alignment with an active area and its associated optical waveguide and a position of each individually defined optical element is based on a position of its associated active area independent of the position of the other plurality of active areas.

148. The optical interconnect module as recited in claim 147, wherein the plurality of active areas are situated on a top surface of the electrooptic component and the wirebond electrical connections make contact with the top surface of the electrooptic component.

149. The optical interconnect module as recited in claim 147 or 148, further comprising an encapsulant covering the plurality of active areas and the wirebond electrical connections and configured such that optical signals emitted by or received by the plurality of active areas pass through the encapsulant.

150. The optical interconnect module as recited in claim 149, wherein the optical engine has an optical engine alignment feature and the optical block subassembly has an optical block subassembly alignment feature aligned to the optical engine alignment feature.

151. The optical interconnect module as recited in claim 150, wherein the optical engine alignment feature directly registers with the optical block subassembly alignment feature to help enable optical alignment between the plurality of active areas and the plurality of optical waveguides.

152. The optical interconnect module as recited in claim 150, further comprising an optical block guide positioned between the optical engine and optical block subassembly, wherein the optical engine alignment feature directly registers with a bottom alignment feature of the optical block guide and the optical block subassembly alignment features directly registers with a top alignment feature of the optical block guide to help enable optical alignment between the plurality of active areas and the plurality of optical waveguides.

153. The optical interconnect module as recited in any one of claims 150-152, wherein the optical block alignment feature or the optical engine alignment feature is fabricated during the same processing step used to fabricate the plurality of individually defined optical elements.

154. The optical interconnect module as recited in any one of claims 149-153, further comprising a transparent substrate situated above the encapsulant, wherein the plurality of individually defined optical elements is situated within or on a surface of the transparent substrate.

155. The optical interconnect module as recited in any one of claims 149-153, wherein the optical block subassembly comprises an optical block and the plurality of individually defined optical elements is situated within or on a surface of the optical block.

156. The optical interconnect module as recited in any one of claims 149-153, wherein the plurality of individually defined optical elements comprises a first set of individually defined optical elements situated within or on a surface of the optical block and a second set of individually defined optical elements situated within or on the surface of the transparent substrate.

157. An optical engine, comprising: a heat sink having a first major surface;an electrooptic component having an active area and wirebond pads, wherein the electrooptic component is mounted to the first major surface and the active area faces away from the first major surface; wirebonds electrically connected to the wirebond pads; a transparent encapsulant covering at least the active area and the wirebonds, the encapsulant defining a top surface; and an individually defined optical element situated on the top surface of the encapsulant or within the encapsulant, wherein the individually defined optical element is optically aligned with the active area and positioned in an optical path extending from or to the active area through the encapsulant.

158. The optical engine of claim 157, wherein the individually defined optical element is situated on the top surface of the encapsulant.

159. The optical engine of claim 158, wherein the individually defined optical element is formed by a surface profile of the top surface of the encapsulant.

160. The optical engine of claim 157, wherein the individually defined optical element is situated within the encapsulant between the active area and the top surface.

161. The optical engine of claim 160, wherein the individually defined optical element comprises a region within the encapsulant having a refractive index different from surrounding portions of the encapsulant.

162. The optical engine of claim 157, further comprising an alignment feature situated on the top surface of the encapsulant or within the encapsulant, the alignment feature being registered relative to the individually defined optical element.

163. An optical engine comprising: a heat sink having a first major surface;an electrooptic component mounted relative to the first major surface, the electrooptic component comprising an active area and a substrate, wherein the electrooptic component is configured for optical signal transmission between the active area and a region spaced from the electrooptic component through the substrate of the electrooptic component, and wherein the substrate of the electrooptic component is substantially transparent at an operating wavelength of the optical signal; and an individually defined optical element situated in the optical path extending through the substrate of the electrooptic component, the individually defined optical element being optically aligned with the active area via said optical path through the substrate of the electrooptic component.

164. A method of assembling an optical engine, the method comprising: providing a heat sink having a first major surface; mounting an electrooptic component relative to the first major surface, the electrooptic component comprising an active area and a substrate substantially transparent at an operating wavelength, wherein the electrooptic component is configured for optical signal transmission between the active area and a region spaced from the electrooptic component through the substrate of the electrooptic component; aligning a processing head of a processing tool with the active area, wherein alignment accounts for the optical signal path extending through the substrate of the electrooptic component; and defining an individual optical element in said optical path using the processing tool, wherein the individual optical element is optically aligned with the active area via the optical signal path through the substrate of the electrooptic component.

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