Patent ID: 12237643

To facilitate understanding, identical reference numerals have been used, where possible, to designate identical elements that are common to the figures. It is contemplated that elements disclosed in one embodiment may be beneficially used in other embodiments without specific recitation.

DESCRIPTION OF EXAMPLE EMBODIMENTS

Overview

One embodiment presented in this disclosure is a device, including: a header disk having a first face with a circumference; a header post that is thermally conductive, the header post having: a second face connected to the first face coterminously with the circumference; a third face opposite to the second face; and a fourth face perpendicular to the second face and the third face; a lens holder, having a fifth face connected to the third face; and an optical subassembly connected to the fourth face and optically aligned with the lens holder.

One embodiment presented in this disclosure is a device, comprising: a header disk having a circumference; a header post that is thermally conductive, the header post having: an arc coterminous to a portion of the circumference; a mounting face, perpendicular to a plane in which the arc and the circumference are defined; and a bonding face perpendicular to the mounting face.

One embodiment presented in this disclosure is a method for constructing a transmitter optical subassembly (TOSA), comprising: bonding a first face of a header disk to a second face of a header post that is thermally conductive, wherein an arc described by a third face of the header post is aligned with a circumference described by a fourth face of the header disk; bonding a fifth face of a lens holder to a sixth face of the header post, opposite to the second face; and bonding a laser sub-mount to a seventh face of the header post, perpendicular to the second face and the sixth face.

Example Embodiments

Existing architectures for coupling a light source to an optical fiber (for transmission to the photonic platform) are generally inefficient at directing heat out or away from the device (e.g., to a heatsink), but these thermal inefficiencies can be ignored if the light source is a low power device. However, as higher power light sources are deployed, greater thermal efficiency is desirable. The present disclosure provides novel heatsinking structures for use with TO-CAN structures. The heatsinking structures discussed herein have larger, and more direct, heat paths than previous heatsinking structures. By establishing more direct contact between the laser and an external element (rather than sealing the header post along with the laser by a cover or other case), the present disclosure provides for improved heat sinking and easier bonding with an external heatsink.

FIGS.1A and1Billustrate an isometric views of the header structure100, according to embodiments of the present disclosure.

InFIG.1A, the header structure100includes a header disk110, a header post120, and one or more electrical leads130a-d(generally or collectively, leads130). The header disk110includes an internal face112that is generally or substantially circular in cross-section, having a circumference111defined by a radius R. A radial face113orbits the internal face112according to the radius R. Although described as generally circular, the present disclosure contemplates that alignment features (e.g., notches, flattened sections) and the manufacturing tolerances can affect the overall “roundness” of the header disk110, without affecting the overall generally circular nature of the header disk110. The header disk110includes one or more through holes to pass the leads130through from one side to the internal face112, and to secure those leads130in place.

InFIG.1B, the header structure100includes a header lip140, a header post120, and one or more electrical leads130a-d. The header lip140includes an internal face142that is generally or substantially semi-circular, having an arc141defined by a radius R. A radial face143orbits the internal face142according to the radius R. Although described as generally semi-circular, the present disclosure contemplates that alignment features (e.g., notches, flattened sections) and the manufacturing tolerances can affect the overall “roundness” of the header lip140, without affecting the overall generally circular nature of the header disk110. The header lip140includes one or more through holes to pass the leads130through from one side to the internal face142, and to secure those leads130in place

The header post120is a thermally conductive component either separately constructed from and later bonded to the header disk110or header lip140(e.g., via a weld joint) or constructed as one piece with the header disk110. The header post120includes a mounting face121, a bonding face122, and an arced face123. InFIG.1A, the header post120includes a connecting face (not illustrated, opposite to the bonding face122) used to connect the header post120and the header disk110. InFIG.1B, the header lip140includes a connecting face (not illustrated, perpendicular to the internal face142) used to connect the header lip140to the mounting face121of the header post120. The mounting face121is at least partially perpendicular to the bonding face122(and the internal face112and/or the connecting face). The arced face123shares the radius R with the circumference111of the header disk110or the arc141of the header lip140so that the arced face123is coterminous with the radial face113/143.

The mounting face121is provided to allow an optical component to mount to the header post120(e.g., via soldering, brazing, welding, wire mounts, adhesives, or pressure/friction mounting). In various embodiments, the header post120is made of Copper (Cu), Stainless Steel, a Copper Tungsten (CuW) alloy, of various alloys including Cu and/or Tungsten (W) to allow for thermal conduction from the mounting face121to the arced face123. Several different potential arrangements of the mounting face122and the arced face123are shown in greater detail in regard toFIGS.2A-2E. In various embodiments, the arced face123is connected to an external heatsink, while in other embodiments, the surface of the arced face123acts as a heatsink to dissipate heat received from the optical component to the surrounding environment.

The electrical leads130provide electrical connections to the optical component, which can include power for the optical component, electrical signals (to convert to optical signals), and feedback signals from the optical component to a controller. Although shown inFIGS.1A and1Bwith four electrical leads130a-d, in various embodiments, more or fewer than four leads130can be used. Additionally, the leads130can include various wires (with or without electrical insulation on various sections) and defined electrical traces, power/signal conduits, and various other non-wire conductors.

FIGS.2A-2Eillustrate various arrangements of an optical subassembly200bonded with a header structure100, according to embodiments of the present disclosure. In some embodiments, the optical subassembly200includes an optical device210, such as a laser diode or other light source, and a sub-mount220that includes various electrical components to control how and when the optical device210generates light based on input electrical signals. In some embodiments, the optical subassembly200includes an optical device210, such as a photodiode or other light detector, and the sub-mount220includes various electrical components to convert light received by the optical device210into output electrical signals. In various embodiments, the optical device210receives an optical signal from an external light source, such as a direct modulated (DM) laser that transmits a pre-modulated optical signal to the optical subassembly200to perform various optical functions on the signal, including: dispersion compensation, wavelength multiplexing, attenuation, or the like.

The arc230described by the arced face123shares a radius R with the circumferences111of the header disk110, but can describe various segment lengths less than, equal to, or greater than 180 degrees in various embodiments. In various embodiments, the bonding face122is semi-circular (as inFIGS.2A and2C) or lunate (e.g., crescent shaped, as inFIGS.2B and2D) to define whether the sub-mount220mounted to the mounting face121is aligned with the center of the header structure100in one or more axes (e.g., on the Y axis forFIGS.2A and2D, on the Y and Z axes forFIGS.2B and2C).

In various embodiments, the sub-mount220can be positioned flush with the mounting face121(as inFIGS.2A and2B) or offset from the mounting face121and may be disposed in a cavity240defined in the mounting face121(as inFIGS.2C and2D) or above the mounting face121on an elevated portion level with the desired height of the laser sub-mount220, such as platform250(as inFIG.2E).

Additionally or alternatively, in some embodiments, the cross-sectional shape of the header post120can vary over the course of the header post120. For example, the arc230can describe less than 180 degrees in a first cross-section and more than 180 degrees in a second cross-section. Similarly, the optical subassembly200can vary in size and position in different cross-sectional views (e.g., having a peg or other projection to fit into a slot defined in the header post120). Accordingly, each of the views shown inFIGS.2A-2Emay be of different header posts120and optical subassemblies200or of different cross-sections of one header post120and optical subassembly200.

FIG.3illustrates an isometric view of the header structure100bonded with a lens holder300, according to embodiments of the present disclosure. The lens holder300(when assembled) includes a lens (not illustrated inFIG.3) in place to focus light generated by the optical subassembly200for transmission onto an optical fiber (not illustrated inFIG.3) or to focus light received from an optical fiber for reception by the optical subassembly200.

The lens holder300is shown inFIG.3as an annular cylinder with a generally circular outer surface301and a generally circular inner surface302, but other shapes besides circles can be used in various embodiments for one or both of the outer surface301and the inner surface302. Additionally, various alignment features on the outer surface301and the inner surface302(e.g., for capturing a lens in place) can be included without affecting the overall generally annular nature of the lens holder300.

The lens holder300is bonded to the bonding face122of the header post120. In various embodiments, the outer surface301of the lens holder300can be coterminous with the arced face123of the header post120. In other embodiments, as shown inFIG.3, the outer surface301of the lens holder300can be offset from the arced face123of the header post120. As shown inFIG.3, the lens holder300is concentrically aligned with the header disk110, however, in various embodiments, the lens holder300may be aligned with an offset on one or more axes from the header disk110.

FIGS.4A and4Billustrate cross-sectional views of the header structure100in different planes to show heat paths400, according to embodiments of the present disclosure.FIG.4Aillustrates a cross-section in the XZ plane, whileFIG.4Billustrates a cross-section in the YZ plane.

Because the header post120is made of a thermally conductive material, and is of the same radius as the header disk110, the arced face123is an external surface of the fully assembled TO-CAN structure. Therefore, the thermally conductive material of the header post120located between the optical subassembly200and the external environment (or an attached external heatsink) provides direct heat paths400for dissipating heat from the optical subassembly200. Stated differently, the heat paths400do not have to travel through the header disk110to dissipate heat from the optical subassembly200, and are provided with the comparatively larger surface area of the arced face123to transfer heat through to the external environment or an external heatsink. Accordingly, the present disclosure provides for improved heatsinking within the same size and shape constraints of TO-CAN or Transmitter Optical Subassembly (TOSA) assemblies that use a header post that is hermetically sealed away from the external environment.

FIGS.5A-5Dillustrate side-views of an assembled TO-CAN structure500, withFIGS.5A,5C, and5Dillustrating external views whileFIG.5Billustrates a cross-sectional side-view of the assembled TO-CAN structure500, according to embodiments of the present disclosure. As assembled TO-CAN structure500includes the header disk110, the header post120, one or more leads130, the optical device210, the sub-mount220, and the lens holder300as described inFIGS.1,2A-2E, and3.

A fiber receptacle510is connected to the lens holder300via a z-sleeve520bonded with the lens holder300. The z-sleeve520provides for alignment freedom when attaching the fiber receptacle to the lens holder300. The fiber receptacle510, in turn, includes an optical fiber570that the fiber receptacle510protects from the environment. In various embodiments, the optical fiber570is designed to carry light generated by the optical device210to another device or optical fiber (e.g., for optical signal processing, multiplexing, de-multiplexing, etc.) or to carry light from an external device to the optical device210. The fiber receptacle510or the fiber570can include insulation and protective coatings, and the optical fiber570can include one or more cores for carrying optical signals.

The fiber receptacle510and the z-sleeve520hold the optical fiber570in place relative to the lens530held by the lens holder300. In turn, the optical fiber570is positioned relative to the lens530and the optical device210so that the lens530can focus incoming or outgoing light between the optical fiber570and the optical device210, ensuring a beam path550is established between the elements. Additionally, the lens530can focus the optical signal to have a different size or mode at each of the optical fiber570and the optical device210.

An optical isolator560, which can include various anti-reflective coatings and filters tuned for various wavelengths, is included in the beam path550. In various embodiments, the optical isolator560is a separate component included in the receptacle510or a standalone component located elsewhere in the beam path550.

In some embodiments, an optional cover540is included in the TO-CAN structure500. As shown inFIGS.5A,5C, and5D, the cover540can be of various lengths (in the X direction) and can encompass various arcs (in a ZY plane) around the lens holder300and/or the header post120. The cover540can be bonded to one or more of the outer surface301of the lens holder300, the header disk110, and the header post120to provide additional protection to the optical subassembly200. In some embodiments, the cover540provides a hermetic seal for a cavity defined by the lens530, lens holder300, header disk110, header post120, and cover540, but can provide a non-hermetic seal or no seal (e.g., as a partial covering not defining a cavity) in other embodiments.

FIG.6A-6Cillustrate assembly of components of a TO-CAN structure500, according to embodiments of the present disclosure.

FIG.6Aillustrates that the connecting face124of the header post120is bonded with a portion of the internal face112of the header disk110to form the header structure100. In various embodiments, one or more joints610are formed at the interfaces of the connecting face124and the internal face112as performed via laser welding, brazing, welding, soldering, or various adhesives to form the header structure100. Although two joints610are illustrated inFIG.6A, more or fewer joints610can be formed in various embodiments. In various embodiments, the header disk110and the header post120can instead be formed as a single-piece (e.g., by removing material from a cylinder to define the internal face112and the mounting face121), thus requiring no joints610to be formed.

FIG.6Billustrates that the optical subassembly200is placed on the mounting face121of the header post120in a desired position before bonding. In various embodiments, pick-and-place die-bonding equipment align and secure the optical subassembly200to the mounting face121. Various connections between the leads130and the sub-mount220can then be formed via soldering, wire-bonding, or the like.

FIG.6Cillustrates a series of joints610that can be formed via laser welding, brazing, welding, soldering, or various adhesives to assembly the TO-CAN structure500. A coaxial welding system can bond the elements together via the joints610. Although six joints610are illustrated inFIG.6C, more or fewer joints610can be formed in various embodiments. For example, when a cover540is included, additional joints610can be formed between the cover540and one or more of the lens holder300, the header disk110, and the header post120.

As illustrated inFIG.6C, a first joint610and a second joint610are formed between the bonding face122of the header post120and the lens holder300to hold the lens holder300and the header structure100together. A third joint610and a fourth joint610are formed between different elements of the receptacle510and the z-sleeve520(e.g., between a fiber “pigtail” and a z-sleeve520) to hold the receptacle510and z-sleeve together, while and a fifth joint610and a sixth joint610formed between the lens holder300and the z-sleeve520hold the components together.

In various embodiments, the joints610are formed as point welds (and additional joints610can be formed in planes beyond the plane illustrated inFIG.6B). In other embodiments, the joints610are formed via continuous welds, in which case the third and fourth joints610can be formed via a single weld and the fifth and sixth joint610can be formed via a (different) single weld (e.g., rotating each weld around the X-axis).

FIG.7illustrates component offsetting for assembly, according to embodiments of the present disclosure. To counteract potential shift or tilt during a laser weld process to form the joints610ofFIG.6Bwhen assembling the TO-CAN structure500, a fabricator can initially apply various offsets between the components so that the finished structure is aligned to form the beam path550between the optical device210and an optical fiber570. To avoid laser hammering when joining components together a fabricator may, due to the asymmetric nature of the TO-CAN structure500, may apply offsets between various components during assembly.

A fabricator can use a receptacle-holder offset710to position the receptacle510, z-sleeve520and the lens holder300out of initial alignment with one another on or more axes so that the receptacle510, z-sleeve520and lens holder300come into alignment (e.g., are concentric and flush with one another) after a laser welding process.

Similarly, a fabricator can use a holder-header offset720to position the lens holder300and the header structure100out of initial alignment with one another on or more axes so that the header structure100and lens holder300come into alignment (e.g., are flush with one another) after a laser welding process. Because the header structure100and the lens holder300are not joined around the entire perimeter of the lens holder300(e.g., due to the generally semi-circular or lunate shape of the bonding face122), the holder-header offset720can include an angled offset. For example, when the bonding face121is disposed in a first plane, the holder-header offset720can position the lens holder300in a second plane that intersects the first plane at a known angle to counter the forces applies during laser welding to “pull” the bonding face121and lens holder300into a flush position where the optical device210is aligned with the lens530after laser welding is complete.

FIG.8is a flowchart of a method800for assembly of a TO-CAN structure500, according to embodiments of the present disclosure. When using a single-piece header structure100, in which the header disk110and header post120are fabricated as one piece, method800begins at block820. Otherwise when using a two-piece header structure100, method800begins a block810, where a fabricator bonds the header disk110with the header post120.

At block810the fabricator bonds the internal face112of the header disk110with the connecting face124of the header post120, for example, via laser welding, brazing, welding, soldering, or an adhesive. When assembled, the arc230described by the arced face123of the header post120is aligned with the circumference111of the header disk110. Stated differently, the arc230and the circumference111share a radius sot that when aligned, the arced face123and the radial face113are coterminous in the portion of the circumference111described by the arc230. In various embodiments, the fabricator position the internal face112at an offset angle relative to the connecting face124at a time of bonding to account for laser hammering, so that the two surfaces are aligned after bonding.

At block820, the fabricator bonds an optical subassembly200to a mounting face121of the header post120. In various embodiments, a solder or wire mount captures a sub-mount220on a planar surface of the mounting face121or in a cavity defined in the mounting face121. The size and position of the sub-mount220on the mounting face121(and any cavities defined therein or platforms defined thereon) position the optical device210of the optical subassembly200at a predefined location to generate or receive optical signals via a beam path550through a lens530.

At block830, the fabricator connects the leads130to the optical subassembly200. The leads130provide electrical pathways to external electrical elements that offer input electrical signals and power to the optical subassembly200, and optionally provide output electrical signal paths from the optical subassembly200. In various embodiments, the leads130are connected to input or output ports of the optical subassembly via wire bonds or solder bonds.

At block840, the fabricator bonds the lens holder300with the header post120(e.g., via laser welding). In various embodiments, one or more joints610are formed between the header post120and the lens holder300(e.g., via laser welding), and the fabricator can position the bonding face122at an offset angle (e.g., a holder-header offset720) relative to the lens holder300to account for laser hammering so that the two surfaces are aligned after bonding.

At block850, the fabricator bonds the lens holder300with the receptacle510. In various embodiments, one or more joints610are formed between the receptacle510and the lens holder300(e.g., via laser welding), and the fabricator can position the components with an offset between each other (e.g., a receptacle-holder offset710) to account for laser hammering so that the two components are aligned after bonding. The lens530included in the lens holder300is aligned with the optical device210mounted to the mounting face121(per block820) to define a beam path550between the lens530and the optical device210, and eventually an optical fiber570(e.g., included per block870).

At block860, a fabricator optionally attaches a cover540to the TO-CAN structure500. In various embodiments, the cover540is bonded to one or more of the internal face112of the header disk110, the radial face113of the header disk110, the outer surface301of the lens holder300, and the arced face123of the header post120. The cover540can form a hermetic seal around the optical subassembly200in a cavity within the TO-CAN structure500, or the cover540can form a non-hermetic seal or a partial seal around the optical subassembly200.

In various embodiments, the various faces of the header post120can be pre-treated to aid in bonding with one or more of the header disk110, the lens holder300, and the cover540. A seed metal applied to the bonding face122, the arced face123, or the connecting face124can aid in brazing, welding, or the application of an adhesive, depending on the bonding method used to secure one or more of the header disk110(per block810), the lens holder300(per block840), or the cover540with the header post120(per block860).

At block870, the fabricator secures an optical fiber570in the receptacle510(e.g., via an epoxy or other adhesive) and installs the TO-CAN structure500into an optical assembly. In various embodiments, the fabricator connects various external electrical wires to the leads130and positions the arced face123of the header post120in contact with an external heat sink. The external heatsink can be in contact via a thermal paste with the arced face123, and the TO-CAN structure500is held in contact with the heatsink via an external case, one or more alignment features, or screw mounts.

In the current disclosure, reference is made to various embodiments. However, the scope of the present disclosure is not limited to specific described embodiments. Instead, any combination of the described features and elements, whether related to different embodiments or not, is contemplated to implement and practice contemplated embodiments. Additionally, when elements of the embodiments are described in the form of “at least one of A and B,” it will be understood that embodiments including element A exclusively, including element B exclusively, and including element A and B are each contemplated. Furthermore, although some embodiments disclosed herein may achieve advantages over other possible solutions or over the prior art, whether or not a particular advantage is achieved by a given embodiment is not limiting of the scope of the present disclosure. Thus, the aspects, features, embodiments and advantages disclosed herein are merely illustrative and are not considered elements or limitations of the appended claims except where explicitly recited in a claim(s). Likewise, reference to “the invention” shall not be construed as a generalization of any inventive subject matter disclosed herein and shall not be considered to be an element or limitation of the appended claims except where explicitly recited in a claim(s).

In view of the foregoing, the scope of the present disclosure is determined by the claims that follow.