CN107533202B

CN107533202B - Optical bench subassembly with integrated photonic device

Info

Publication number: CN107533202B
Application number: CN201680023080.XA
Authority: CN
Inventors: R.R.瓦兰斯; S.李
Original assignee: Nanoprecision Products Inc
Current assignee: Nanoprecision Products Inc
Priority date: 2015-03-22
Filing date: 2016-03-22
Publication date: 2021-01-15
Anticipated expiration: 2036-03-22
Also published as: IL254364A0; WO2016154229A1; CA2978955A1; RU2717374C2; AU2016235324B2; JP2018509655A; AU2016235324A1; BR112017019567A2; EP3274108A1; CN107533202A; JP6898245B2; RU2017136256A; KR20170129236A; MX2017012155A; RU2017136256A3

Abstract

An optical bench subassembly including an integrated photonic device is disclosed. Optical alignment of the optoelectronic device with the optical bench can be performed outside the optoelectronic package assembly prior to attaching the photonic device to the optoelectronic package assembly. The photonic device is attached to the base of the optical bench with its optical input/output optically aligned with the optical output/input of the optical bench. The optical bench supports the array of optical fibers in a precise relationship with respect to the structured reflective surface. The photonic device is mounted on the submount to be attached to the optical bench. The photonic device may be actively or passively aligned with the optical bench. After optical alignment is achieved, the submount of the photonic device is fixedly attached to the base of the optical bench. The optical bench subassembly can be structured to be hermetically sealed as a hermetic feedthrough for hermetic attachment to a hermetic optoelectronic package.

Description

Optical bench subassembly with integrated photonic device

Background

1. Priority claim

The application:

(1) priority is claimed for U.S. provisional patent application No. 62/136, 601 filed 3/22/2015;

(2) a continuation-in-part application, U.S. patent application No. 13/861, 273 filed on 11/4/2013, which continues for:

(a) U.S. provisional patent application No. 61/623, 027, filed on day 11, 4/2012,

(b) claim priority from U.S. provisional patent application No. 61/699, 125 filed on 9, 10, 2012, and

(c) a continuation-in-part application, U.S. patent application No. 13/786, 448, filed on 3/5/2013, claiming priority from provisional patent application No. 61/606, 885, filed on 3/5/2012.

(3) Continuation is a continuation of the part of us patent application No. 14/714, 211 filed on 15/5/2015, which continues to apply:

(a) priority is claimed for U.S. provisional patent application No. 61/994, 094,

(b) is part of a continuation-in-part application No. 14/695, 008 of us patent application No. 2015, 4-month, 23.

These applications are fully incorporated by reference as if fully set forth herein. All publications described below are incorporated by reference in their entirety as if fully set forth herein.

2. Field of the invention

The present invention relates to optical bench-based sub-assemblies, and more particularly to optical bench-based, fiber optic sub-assemblies, and more particularly to optical bench-based, hermetic fiber feedthrough sub-assemblies.

3. Description of the Prior Art

There are many advantages to transmitting optical signals via fiber optic waveguides and their use is diverse. Single and multiple fiber waveguides can be used simply to transmit visible light to a remote location. Complex telephone and data communication systems can transmit a plurality of specific optical signals. Data communication systems involve devices that couple optical fibers in end-to-end relationship, including optoelectronic or photonic devices that include optical and electronic components that provide, detect, and/or control light to convert between optical and electrical signals.

For example, a transceiver (Xcvr) is an optoelectronic module comprising a transmitter (Tx) and a receiver (Rx) combined with circuitry within a module housing, which is known in the art as an enclosure. The package may be hermetically sealed to protect its contents from the environment. The transmitter includes a light source (e.g., a VCSEL or DFB laser) and the receiver includes a light sensor (e.g., a Photodiode (PD)). Heretofore, the circuitry of the transceiver (e.g., including the laser driver, the transimpedance amplifier (TIA), etc.) has been soldered onto a printed circuit board. Such transceivers generally have a substrate (hermetic or non-hermetic) forming the bottom or base of the package, and then optoelectronic devices such as lasers and photodiodes are soldered to the substrate. The optical fiber is connected to the exterior of the package or passes through the wall of the package using a hermetic feedthrough (see US20130294732a1, commonly assigned to the assignee/applicant of the present application and fully incorporated as if fully set forth herein).

The end of the optical fiber is optically coupled to an optoelectronic device held in the enclosure. The feed-through element supports a portion of the optical fiber that passes through the wall opening. For many applications, it may be desirable to hermetically seal the optoelectronic device within the housing of the optoelectronic module to protect the components from corrosive media, moisture, and the like. Since the encapsulation of the optoelectronic module as a whole has to be hermetically sealed, the feed-through elements have to be hermetically sealed so that the optoelectronic components within the optoelectronic module housing are reliably and continuously protected from environmental influences.

For proper operation, optoelectronic devices supported on printed circuit boards require efficient coupling of light to external optical fibers. Some optoelectronic devices require single mode optical connections that require tight alignment tolerances between the optical fiber and the device, typically less than 1 micron. This is particularly challenging for multiple fiber applications where multiple fibers need to be optically aligned to multiple optoelectronic devices using active optical alignment methods where the position and orientation of the fiber(s) is adjusted by mechanical means until the amount of light transferred between the fiber and the optoelectronic device is maximized.

Fig. 1A and 1B illustrate a hermetically sealed optoelectronic package 500 having a hermetic multi-fiber feedthrough 502, where the hermetic feedthrough 502 is actively aligned with a photonic device 504 mounted on a submount 506 supported by the bottom of the package 500. In this example, the feedthrough 502 is similar to the optical coupling device disclosed in US2016/0016218a1, US2016/0016218a1 has been commonly assigned to the assignee/applicant of the present application, and is fully incorporated as if fully set forth herein. The photonic device 504 may include a VCSEL array and/or a PD array supported on the package bottom, for example, via a submount 506 and a printed circuit board 508. Printed circuit board 508 provides other electronic components and circuitry, and package 500 may include several printed circuit boards. After the photonic device 504/submount 506 and other components are assembled into the package 500, the feedthrough 504 is inserted through an opening 503 defined by the nozzle 50 on the sidewall of the housing 501 of the package 500. The array of optical fibers 20 of the optical cable 21 is supported by the feedthrough 502 and is actively aligned with the photonic device 504 to achieve a desired optical coupling efficiency between the photonic device and the array of optical fibers 20. This process requires that the photonic device 504 and associated electronics (not shown) be pre-assembled into the package 500. The photonic device 504 is activated/stimulated to transmit/receive optical signals 22 to/from the array of optical fibers 20. In essence, the optical signal to/from the optical fiber 20 is optimally coupled to the photonic device 504 when the signal 22 transmitted between the optical fiber 20 and the photonic device 504 is maximized. The feedthrough 502 is then brazed into the nozzle 50 at the package side wall of the housing 501 in an optically aligned state.

Active optical alignment involves a relatively complex, low-throughput process, since either the VCSEL or the PD must be excited during the active alignment process. Manufacturers of integrated circuits typically have expensive capital equipment capable of sub-micron alignment (e.g., wafer probers and handlers for testing integrated circuits), while companies that package chips typically have less capable mechanical equipment (several micron alignment tolerances, not typically applicable to single mode equipment) and often use manual operations.

The current state of the art is expensive due to the inclusion of the package, in addition to the usual electronics use and assembly processes, and/or is often not suitable for single mode applications. The package is a relatively more expensive component (which includes expensive circuit components, such as ICs, etc.) relative to the hermetic feedthrough subassembly. Given that the required pre-assembly of the components supporting the active optical alignment in the pre-assembled package is required and further given that the active alignment and soldering process involves steps with a high risk for the end of the overall packaging process, the failure to achieve active alignment due to defective components, which may be introduced in the active alignment process, will result in the entire package including the photonic device and other components already packaged therein being discarded.

Furthermore, while VCSEL and PD components can be tested in a static state prior to assembly, they cannot be tested in an operational state until after as the electronics to drive these components are assembled in a package. Thus, the aging process of VCSEL and PD components (to identify early-life components as disqualified from simulated loading conditions) can be performed only after these components are assembled into a package. This will result in further waste of packages that are assembled relatively more expensive modules (i.e., low package yield) due to defective but relatively inexpensive VCSEL and PD components. VCSEL and PD assemblies are known to contribute to a relatively high number of rejects of the assembled packages.

An additional reject pattern that results in wasted assembled packages is caused by a relatively larger and more compliant structural ring (represented by the dashed line in fig. 1B) that maintains optical alignment between the photonic device and the feedthrough, as shown in fig. 1B. Long structural loops are more sensitive to thermo-mechanical deformation (which can cause the package to deviate outside of expected design specifications), thereby resulting in failure modes.

There is a need for improved structures to optically align the input/output ends of optical fibers to be coupled to optoelectronic components/photonic devices that improve throughput, tolerances, manufacturability, ease of use, functionality, and reliability at reduced cost.

Disclosure of Invention

The present invention provides an improved structure for facilitating optical alignment of a photonic device to an optical bench that overcomes the disadvantages of the prior art. The present invention combines a photonic device and an optical bench in a subassembly such that optical coupling of the photonic device to the optical bench can occur outside of the optoelectronic package assembly.

According to the invention, the photonic device is attached to the base of the optical bench with its optical input/output optically aligned with the optical output/input of the optical bench.

In one embodiment, the optical bench supports an optical component in the form of an optical waveguide (e.g., an optical fiber). In a more particular embodiment, the base of the optical bench defines an alignment structure in the form of at least one groove to accurately support the end portion of the optical fiber. Optical elements (e.g., lenses, prisms, reflectors, mirrors, etc.) can be provided in precise relation to the end faces of the optical fibers. In another embodiment, the optical element includes a structured surface, which may be a flat reflective surface or a concave reflective surface (e.g., an aspherical mirror surface).

In one embodiment, the photonic device may be mounted on a submount that is attached to the base of the optical bench in optical alignment with the optical bench. The submount may be provided with circuitry, electrical contact pads, circuit components (e.g., drivers for VCSELs, TIAs for PDs), and other components and/or circuitry associated with the operation of the photonic device.

The photonic device may be passively aligned with the optical bench (e.g., depending on alignment marks disposed on the optical bench). Alternatively, the photonic device and the optical bench may be actively aligned by passing an optical signal between an optical waveguide in the optical bench and the photonic device. The photonic devices (e.g., VCSELs and/or PDs) can be activated to allow active alignment with optical waveguides (e.g., optical fibers) supported in the optical bench without relying on other components within the package. After optical alignment is achieved, the submount of the photonic device is fixedly attached to the base of the optical bench.

The base of the optical bench is preferably formed by stamping a ductile material (e.g., metal) to form the precise geometry and features of the optical bench. The optical bench subassembly can be structured to be hermetically sealed.

In another embodiment of the present invention, the optical bench is structured to support a plurality of waveguides (e.g., a plurality of optical fibers) and a structured reflective surface (e.g., an array of mirrors) to work with an array of photonic devices (VCSELs and/or PDs) mounted on the submount.

The present invention preassembles optical elements and components and photonic devices into an optical bench subassembly precisely prior to assembly into a larger optoelectronic package. The sub-assemblies may be functionally tested at the sub-assembly level, including burn-in testing, outside of the optoelectronic package, thereby reducing waste of more expensive optoelectronic packages due to early failure of photonic devices assembled in the optoelectronic packages.

Drawings

For a fuller understanding of the nature and advantages of this invention, as well as the preferred mode of use, reference should be made to the following detailed description read in conjunction with the accompanying drawings. In the following drawings, like reference characters designate like or similar parts throughout the several views.

FIG. 1A illustrates a hermetic optoelectronic package including a hermetic optical fiber feedthrough; FIG. 1B is a cross-sectional view taken along line 1B-1B of FIG. 1A.

Fig. 2A shows an optical bench subassembly in the form of a hermetic feedthrough including an integrated optoelectronic device according to one embodiment of the present invention; fig. 2B is a cross-sectional view taken along line 2B-2B in fig. 2A, shown installed in a hermetic optoelectronic package.

Fig. 3A is an enlarged view of an optical bench of the optical bench subassembly of fig. 2, according to one embodiment of the present invention; fig. 3B is an assembled view of the optical bench.

Fig. 4A is an enlarged view of an optical bench in an optical bench subassembly according to another embodiment of the present invention; fig. 4B is an assembled view of the optical bench.

Fig. 5 illustrates an alternative embodiment of a submount for a photonic device in an optical bench subassembly.

Fig. 6A to 6C show an assembly sequence of hermetic optoelectronic packages, wherein fig. 6A illustrates the assembly of a photonic assembly; FIG. 6B illustrates the assembly and active alignment of the photonic component with the optical bench; fig. 6C illustrates the assembly of the hermetic optoelectronic package.

Fig. 7 illustrates a hermetic feedthrough installed in a hermetic optoelectronic package.

Detailed Description

The invention is described below with reference to various embodiments with reference to the accompanying drawings. While this invention is described in terms of the best mode for achieving this invention's objectives, it will be appreciated by those skilled in the art that variations may be accomplished in view of these teachings without deviating from the spirit or scope of the invention.

The present invention provides an improved structure that facilitates optical alignment of a photonic device to an optical bench that overcomes the shortcomings of the prior art. The present invention combines a photonic device and an optical bench in a subassembly such that optical coupling alignment of the photonic device and the optical bench can be performed outside of the optoelectronic package assembly.

According to the invention, the photonic device is attached to the base of the optical bench with its optical input/output optically aligned with the optical output/input of the optical bench. Various embodiments of the present invention incorporate some of the inventive concepts developed by the assignee of the present invention (nanoPrecision Products, Inc.), including various proprietary Products (including optical bench subassemblies used in connection with optical data transmission), including concepts disclosed in the patent publications discussed below (which have been commonly assigned to the assignee). Priority of the pending application is already claimed herein.

For example, U.S. patent application publication No. US2013/0322818a1 discloses an optical coupling device for routing optical signals in the form of an optical bench having a stamped structured surface for routing optical data signals. The optical bench includes a metal base having a structured surface defined therein, wherein the structured surface has a surface profile that bends, reflects, and/or reshapes incident light. The base also defines an alignment structure configured with surface features to facilitate precise positioning of an optical component (e.g., an optical fiber) on the base in precise optical alignment with the structured surface to allow transmission of light along a defined path between the structured surface and the optical component, wherein the structured surface and the alignment structure are integrally defined on the base by stamping a ductile metallic material to form an optical bench.

US patent application publication US2015/0355420a1 also discloses an optical coupling device for routing optical signals, in particular in the form of an optical bench, for use in an optical communication module, wherein a structured surface having a surface profile that bends, reflects and/or reshapes incident light is defined on a metal base. An alignment structure is defined on the base, configured with surface features to facilitate positioning of an optical component (e.g., an optical fiber) on the base in alignment with the structured surface to allow light to travel along a defined path between the structured surface and the optical component. The structured surface and the alignment structure are integrally defined on the base by stamping a ductile metallic material of the base. The alignment structure facilitates passive alignment of the optical component on the base in optical alignment with the structured surface to allow light to travel along a defined path between the structured surface and the optical component.

US patent application publication US2013/0294732a1 also discloses a hermetic optical fiber alignment assembly with integral optical elements, in particular a hermetic optical fiber alignment assembly comprising an optical bench including a metal ferrule portion having a plurality of grooves for receiving optical fiber end portions, wherein the grooves define the positioning and orientation of the end portions with respect to the ferrule portion. The assembly includes an integral optical element for coupling the input/output ends of the optical fibers to optoelectronic devices in the optoelectronic module. The light element may be in the form of a structured reflective surface. The end of the optical fiber is at a defined distance from and aligned with the structured reflective surface. The structured reflective surface and the fiber alignment groove may be formed by stamping a ductile metal to define these features on a metal base.

U.S. patent No. 9,213,148 also discloses a similar hermetic fiber alignment assembly, but does not require an integral structured reflective surface.

U.S. patent No. 7,343,770 discloses a novel precision stamping system for manufacturing small tolerance parts. Such an inventive stamping system may be implemented in various stamping processes to produce the devices disclosed in the above-described patent publications. These stamping processes involve stamping large volumes of material (e.g., metal blanks) to form the final overall geometry and geometry of the surface features, including the reflective surface having a desired geometry that is precisely aligned with other defined surface features, with tight (i.e., small) tolerances.

U.S. patent application publication No. US2016/0016218a1 also discloses a composite structure including a base having a main portion and an auxiliary portion of dissimilar metal material. The base and the auxiliary portion are formed by stamping. When the auxiliary portion is stamped, it interlocks with the base and, at the same time, forms the desired structured features, such as structured reflective surfaces, fiber alignment features, etc., on the auxiliary portion. With this approach, relatively less critical structured features may be shaped over the volume of the base with less effort to maintain relatively greater tolerances, while relatively more critical structured features on the secondary portion are more precisely shaped to further account for sizing, geometry, and/or finish under relatively smaller tolerances. The secondary portion may include an additional composite structure having two dissimilar metallic materials associated with different properties for stamping different structured features. This stamping method improves the earlier stamping process in U.S. patent No. 7,343,770, wherein the bulk material subjected to stamping is a homogenous material (e.g., a metal strip such as Kovar, aluminum, etc.). The stamping process produces structural features out of a single homogeneous material. Thus, the different features will have in common the properties of the material, which may not be optimized for one or more of the features. For example, having properties suitable for stamping alignment features may not have properties suitable for stamping reflective surface features having optimal light reflection efficiency to reduce optical signal loss.

Us patent 8,961,034 discloses a method of producing a ferrule for supporting an optical fiber in an optical fiber connector, comprising stamping a metal blank to form a body having a plurality of generally U-shaped, longitudinally opening grooves, each groove having a longitudinal opening disposed on a surface of the body, wherein each groove is sized to securely retain the optical fiber in the groove by gripping the optical fiber. The optical fiber is securely retained in the body of the ferrule without the need for additional fiber retaining members.

PCT patent application publication No. WO2014/011283a2 discloses ferrules for fiber optic connectors that overcome many of the disadvantages of prior art ferrules and connectors and further improve upon the pin-less alignment ferrules described above. The fiber optic connector includes a fiber ferrule having a generally elliptical cross-section for aligning an array of a plurality of optical fibers with optical fibers held in another ferrule using a ferrule.

The above inventive concepts are incorporated herein by reference and will be referenced below in order to facilitate disclosure of the present invention. Exemplary embodiments of hermetic optical fiber feedthroughs for hermetic optoelectronic packages are disclosed that include an optical bench subassembly having an integrated photonic device.

Fig. 2A and 2B illustrate one embodiment of a sealed fiber optic feedthrough in the form of an optical bench subassembly 10 that includes an optical bench 11 with an integrated photonic device 12 in accordance with one embodiment of the present invention. In the illustrated embodiment, photonic device 12 is mounted on submount 14 at a position aligned with the optical input/output of optical bench 11 (see optical signal 22 in fig. 2B), submount 14 being attached to optical bench 11.

Fig. 3A and 3B more clearly illustrate the structure of the optical bench 11 in the optical bench subassembly 10. In this embodiment, optical bench 11 is similar to the hermetic multi-fiber alignment sub-assembly disclosed in US2016/0016218A1 of the assignee referenced above. The optical bench supports one or more optical waveguides of a plurality of optical fibers 20, which in the illustrated embodiment are optical cables 21. For the case of multiple optical fibers, the base 13 of the optical bench 11 defines multiple open grooves 16 that support the optical fibers 20 and defines or supports optical elements (e.g., lenses, prisms, reflectors, mirrors, etc.). In the illustrated embodiment, the optical element comprises an array of structured reflective surfaces 17, one optical fiber 20 for each structured reflective surface 17. The reflective surface may be a flat reflective surface or contoured as a concave reflective surface (e.g., an aspherical mirror surface) or a convex reflective surface. In the illustrated embodiment, the base 13 comprises a composite structure including a secondary portion 30 of a material dissimilar to that of the remainder of the base 13 (i.e., the primary portion 13'). The base 13, including the secondary portion 30, is stamped from a malleable material to form the body geometry and desired surface features. In this case, the auxiliary portions are formed by stamping a ductile metallic material to form the array of structured reflective surfaces 17 and grooves 18, while the base 13 is stamped from a different ductile metallic material to form the grooves 16 and other structures shown. As disclosed in US2016/0016218a1, when the auxiliary portion 17 is stamped, it interlocks with the base 13, resembling a rivet, and simultaneously forms the desired structured features on the auxiliary portion 30, including the array of structured reflective surfaces 17 and the fiber alignment grooves 18 for supporting the end portions of the optical fibers 20, so that the end faces (i.e., input/output ends) of each reflective surface 17 and the corresponding optical fiber 20 maintain a precise relationship. In this embodiment, the secondary portion 17 and the primary portion 13' are stamped using dissimilar metal materials.

Open grooves

16 and 18 may be configured and formed in accordance with the stamped open grooves disclosed in U.S. patent No. 8,961,034, which securely clamps the optical fiber in the groove without the need for additional fastening members (e.g., without epoxy, etc.). In the illustrated embodiment, the cover 15 is provided to cover the base 13 without covering the structured reflective surface 17. A hermetic sealing epoxy (e.g., glass epoxy) is applied to fill the space around the portion of the optical fiber 20 in the cavity 19 between the lid 15 and the base 13 to form a hermetic seal such that the optical bench 11 is a feedthrough that can be used with an optoelectronic package with similar functionality as the hermetic feedthrough 502 of fig. 1, except that the optical bench 11 has an optoelectronic device integrated thereon to form the optical bench assembly 10 according to the present invention. A further elaboration of a similar gastight feedthrough structure can be found in US2013/0294732 a.

Fig. 4A and 4B illustrate another embodiment of an optical bench 11' similar to the optical bench 11 of fig. 3A and 3B, except for the optical cable 21. In this embodiment, the optical bench 11' is provided with a detachable connection in the form of a ferrule 30. Instead of the optical fiber 21 extending away from the optical bench 11 ', the ferrule 30 supports the proximal cross-section of a short portion of the optical fiber 20, while the distal front portion of the optical fiber is supported by the

grooves

16 and 18 in the optical bench 11'. The ferrule 30 may be structured to have a generally elliptical cross-section as disclosed in WO2014/011283a 2. A sleeve (not shown) may be used to couple to a fiber optic cable (e.g., a patch cable), for example, terminated with a similar ferrule. In this embodiment, if the stub cable becomes defective, it can be disconnected and replaced without replacing the entire optoelectronic package to which the optical bench 11' is permanently or fixedly attached.

Turning now to the photonic device, in the illustrated embodiment of fig. 2A and 2B, the photonic device 12 is mounted to the submount 14 to form a photonic device assembly 23. The submount 14 may be provided with circuitry, electrical contact pads, circuit components (e.g., drivers for VCSELs, TIAs for PDs), and other components and/or circuitry associated with the operation of the photonic device 12.

Fig. 6A to 6C illustrate an assembly sequence of the hermetic photoelectric package. FIG. 6A illustrates the assembly of a photonic (transmitter or receiver or transceiver) assembly; FIG. 6B illustrates the assembly and active alignment of the photonic component with the optical bench; fig. 6C illustrates the assembly of the hermetic optoelectronic package.

Referring to fig. 6A, in the case where photonic device 12 is a transmitter (such as a VCSEL), it is mounted on sub-mount 14 along with a driver chip. The VCSELs may be wire bonded to circuitry on submount 14. Testing may be performed after assembly to confirm that the VCSEL is operable to transmit an optical signal. In the case where the photonic device 12 is a receiver (such as a PD) it is mounted on a submount 14 together with a TIA chip. The PD may be wire bonded to circuitry on the sub-mount 14. Testing may be performed after assembly to confirm that the PD is operable to receive the optical device and output an electrical signal. In the case of a transceiver, the above procedures are combined to test separate receive and transmit functions. The photonic device 12 may include a plurality of receivers, transmitters and/or transceivers mounted on the submount 14.

Referring to fig. 6B, submount 14 of the photonic device assembly is attached to the opposing surface of base 13 of optical bench 11 in a position where photonic device 12 is optically aligned with optical bench 11 (in which position the input/output ends of photonic device 12 are optically aligned with the output and input ends of optical bench 11) so that optical path 12 achieves the desired optical coupling efficiency between the photonic device and optical fiber 20. In the embodiment illustrated in fig. 2B, optical path 22 is between the end face of the input/output end of optical fiber 20 and the output/input end of corresponding optical device 12, which optical path 22 is bent and reshaped by reflective surface 17 (e.g., an aspherical mirror surface). More specifically, in the illustrated embodiment, the optical path is in a direction out of the plane of the base 13 that is generally perpendicular to the plane of the base 13. As shown in fig. 2B, the plane of the sub-mount 24 is parallel to the plane of the base 13. The frame 32 is provided as a spacer between the opposing surfaces of the submount 14 and the base 13 to provide a space between the submount 14 and the base 13 to accommodate the photonic device 13. In the illustrated embodiment, there are four arrays of reflective surfaces 17 corresponding to the four arrays of optical fibers 20.

The photonic device 12 may be passively aligned with the optical bench 11 (e.g., by relying on alignment marks (not shown) provided on the base of the optical bench 11). Alternatively, photonic device 12 and optical bench 11 may be actively aligned by transmitting an optical signal between an optical waveguide (i.e., optical fiber 20) in optical bench 11 and photonic device 12 and measuring the intensity of the optical signal in the optical path to determine an optical coupling that indicates an optical alignment state. Photonic device 12 (e.g., VCSEL and/or PD) can be activated to allow active alignment with an optical fiber supported in optical bench 11 without relying on other components within the optoelectronic package to which optical bench assembly 10 is mounted. For example, where the optoelectronic device 12 is a transmitter (e.g., a VCSEL), it is energized to emit light toward the reflective surface 17 for orientation to the end face of the corresponding optical fiber 20. The intensity of the optical signal transmitted via the reflective surface 17 and through the corresponding optical fiber is measured to determine the optical coupling between the transmitter and the optical bench 11. In case the optoelectronic device is a receiver (e.g. a PD), the optical signal reflected by the reflective surface to the corresponding receiver is supplied through an optical fiber. The degree of optical coupling between the optical fibre and the receiver can be determined from the electrical output of the receiver (which corresponds to the strength of the received optical signal) to identify the alignment condition. The active alignment process involves moving the photonic device 12 in the plane of the submount 14 with respect to the reflective surface 17 while determining the optical coupling efficiency for the alignment point. To facilitate electrical connection to perform active alignment, conductive pads are provided on the surface of the submount remote from the base 13.

Once the desired optical alignment is achieved, submount 14 of photonic device 12 is fixedly attached to the base of the optical bench, for example by laser welding, soldering, or epoxy.

After the optical bench subassembly 10 is assembled, it may be aged to eliminate early life failures and further functionally tested.

The previous embodiment of the optical bench subassembly 10 including the integrated photonic device 12 is a hermetic feedthrough with the integrated photonic device 12.

Referring to fig. 6C, and as shown in fig. 2B, once the assembly of the optical bench subassembly 10 is completed, the optical bench subassembly 10 is hermetically attached (e.g., by soldering) to an optoelectronic package 500', which may be similar to the package 500 of fig. 1A, except that the photonic device 12 is integrated into the optical bench subassembly 10 in optical alignment with the optical bench 11. The optoelectronic package 500' is provided with various components (e.g., IC, chip, submount, circuit board, etc.). The optical bench subassembly 10, which is a hermetic feed-through, is inserted through the opening of the nozzle 50 in the sidewall of the housing 501 'of the seal 500' and hermetically sealed (e.g., by brazing). The location of the feedthrough with respect to the seal 500 'is not critical compared to the case of fig. 1B, as there is no optical alignment required between the feedthrough and the external photonic device within the package 500'. As shown in fig. 2B, the submount 14 may be solder bonded to a printed circuit board 39 (which may be a flexible printed circuit board) within the package 500' with vias 36 disposed through the substrate of the submount 14 to connect to the photonic device 12 on the other side of the submount 14. A Ball Grid Array (BGA) with micro-solder ball joints may be disposed on the submount 14. Other electrical connections may include the optical bench subassembly 10 ' in the embodiment of fig. 5, in which the surrounding traces 38 disposed on the sides of the submount 14 ' are electrically connected to a circuit board (not shown) in the package 500 ' by wire bonds or flexible circuit joints 37. Alternatively, spring pins (not shown) may be configured to form an electrical connection between the submount and the printed circuit board in the package 500'. These electrical connections absorb the error motions and stresses due to thermal expansion/contraction, which will not affect the optical alignment between the photonic device integrated on the board and the optical bench in the optical bench subassembly.

Fig. 7 illustrates hermetic feedthrough/optical bench subassembly 10 mounted in hermetic optoelectronic package 500'. Other electronics and circuit components are omitted from the view of fig. 7. The hermetic cover of hermetic optoelectronic package 500' is also omitted from the illustration.

After assembling the optical bench subassembly 10 to the hermetic optoelectronic package 500 ', the package 500' may be aged to eliminate early life failures and further functionally tested.

Given that the present invention pre-assembles optical elements and components and photonic devices into an optical bench subassembly precisely prior to assembly into a larger optoelectronic package, the optical bench subassembly can be functionally tested at the subassembly level, including burn-in testing, outside of the optoelectronic package, thereby reducing waste of more expensive optoelectronic packages (including expensive circuit components, such as ICs and the like) due to early failure of photonic devices mounted in the optoelectronic package. The active alignment process of the optical bench subassembly is much easier. In addition, a much smaller and more robust structural ring is provided between the optical bench and the photonic device. Thereby, for an optoelectronic package comprising a hermetic feed according to the present invention, an overall higher yield, higher reliability and lower manufacturing costs may be achieved.

While the invention has been particularly shown and described with reference to a preferred embodiment, it will be understood by those skilled in the art that various changes in form and detail may be made therein without departing from the spirit, scope and teaching of the invention. Accordingly, the disclosed invention is to be considered merely as illustrative and limited in scope only as specified in the appended claims.

Claims

1. An optical bench subassembly for routing optical signals, comprising:

an optical bench comprising:

a base;

a structured reflective surface defined on a surface of the base, wherein the structured reflective surface has a surface profile that reshapes and bends incident light;

an optical fiber; and

an optical fiber alignment groove defined on a surface of the base configured to position the optical fiber on the base in optical alignment with the structured reflective surface, thereby allowing an optical signal to be transmitted along a defined optical path between the structured reflective surface and the optical fiber, wherein the optical path extends from the structured reflective surface out of the base; and

a lid hermetically attached to the base at a side having a fiber alignment groove to hermetically seal the space around the fiber portion, wherein the lid does not extend to cover the structured reflective surface, thereby forming a hermetic feedthrough; and

a photonic device assembly comprising a submount and a photonic device mounted on the submount, wherein the submount is attached to a base of an optical bench with the photonic device facing the structured reflective surface and optically aligned to the structured reflective surface along an optical path, wherein the submount comprises electrical connections for mounting to an external circuit, wherein the submount is pre-attached to the base of the optical bench prior to mounting to the circuit and the photonic device is optically aligned to the structured reflective surface.

2. The optical bench subassembly as in claim 1, further comprising an array of optical fibers and an array of structured reflective surfaces corresponding to the array of optical fibers.

3. The optical bench subassembly as in any one of claims 1-2, wherein the photonic device is passively aligned to the structured reflective surface when the submount is pre-attached to the base of the optical bench prior to mounting to the circuit.

4. The optical bench subassembly as in any one of claims 1-2, wherein the photonic device is actively aligned to the structured reflective surface when the submount is pre-attached to the base of the optical bench prior to mounting to the circuit.

5. The optical bench subassembly as in any one of claims 1-2, wherein the structured reflective surface and the corresponding fiber alignment groove are integrally defined on the base by stamping the ductile material of the base, wherein the structured reflective surface is structured to reshape light to couple the input/output end of the optical fiber and the photonic device without relying on a refractive optical element between the input/output end of the optical fiber and the photonic device.

6. A hermetic optoelectronic package comprising:

a housing having an opening sized to receive an optical bench of an optical bench subassembly according to any preceding claim;

an electronic component and a circuit disposed within the housing; and

an optical bench of the optical bench subassembly is hermetically attached to the opening of the housing, a structured reflective surface of the optical bench is optically aligned with a photonic component assembly within the optical bench subassembly, wherein the sub-bench is mounted to the electrical circuit via the electrical contacts.

7. The hermetic optoelectronic package as in claim 6, wherein the optical bench subassembly is functionally tested prior to hermetically sealing to the housing.

8. A method of forming a hermetic optoelectronic package, comprising:

providing a housing having an opening sized to receive an optical bench of an optical bench subassembly according to any one of claims 1-6;

disposing the electronic component and the circuit within the housing;

after the optical bench is optically aligned with the photonic assembly within the optical bench subassembly, the optical bench of the optical bench subassembly is hermetically attached to the opening of the housing.

9. The method of claim 8, wherein the optical bench subassembly is functionally tested, including burn-in testing, prior to hermetically attaching the optical bench to the housing with the structured reflective surface of the optical bench in optical alignment with the photonic assembly within the optical bench subassembly.