Systems and methods for reconfigurable micro-optic assemblies

A micro-optics assembly and a method for assembling the micro-optics assembly are provided. The micro-optics assembly may include an optical bench having an opening, a cylindrical body disposed in the opening and having a solder well, a heating element thermally coupled to the solder well, and an optical element. The optical element may include a frame having a post and a micro-optic mounted in the frame. The post may be secured in a solid solder material disposed within the solder well in the cylindrical body. The solder may be reflowable such that the micro-optics assembly is reconfigurable without the need for optical realignment components permanently mounted to the optical bench.

Not applicable.

FIELD

The disclosure relates in general to optical systems, and in particular to, for example, without limitation, a configurable optical bench for micro-optics positioning and alignment.

BACKGROUND

The description provided in the background section, including without limitation, any problems, features, solutions or information, should not be assumed to be prior art merely because it is mentioned in or associated with the background section. The background section may include information that describes one or more aspects of the subject technology.

Photonic integrated circuits formed in semiconductor substrates are sometimes used to modify or process optical signals. However, in various applications, such as applications in which mixed materials are used or high optical power is desired, photonic integrated circuits cannot be used and micro-optic systems with micro-optics mounted to an optical bench are sometimes used.

However, conventional micro-optic systems with micro-optics mounted to an optical bench are limited in that fine-pitch tip/tilt optic adjusters and associated fine-pitch adjustment screws must be included in the assembly to align each micro-optic and then must remain on the optical bench to constrain the desired position of the optics for the life of the assembly. The fine-pitch tip/tilt optic adjusters and associated fine-pitch adjustment screws can be bulky, particularly in comparison to the size of the micro-optic, and therefore limit the fill factor of the micro-optic system, add undesirable weight and size to the micro-optic system, and typically limit the size of the micro-optics to greater than twelve millimeters in diameter.

SUMMARY

In accordance with various aspects of the subject disclosure, the systems, methods, and combinations of materials described herein enable mounting and alignment of micro-optics in a micro-optics assembly with a high-density fill factor, while allowing the alignment of the micro-optics to be re-adjusted after an initial micro-optic position is set. The fill factor may be as much as, or greater than, 25 optics per square inch (for example). The systems, methods, and combinations of materials described herein include an optical bench on which micro-optics as small as, or smaller than, 2-3 millimeters (mm) in diameter can be mounted, aligned, and re-aligned if desired. Furthermore, the systems, methods, and combinations of materials described herein enable alignment of the micro-optics to be stable over temperature excursions of, for example, −40 C to +70 C. The alignment may be stable over these temperature ranges to within an accuracy of, for example, less than 20 arcseconds.

In accordance with various aspects of the subject disclosure, a micro-optics assembly is provided that includes an optical bench having an opening. The micro-optics assembly also includes a cylindrical body disposed in the opening and having a solder well. The micro-optics assembly also includes a heating element thermally coupled to the solder well. The micro-optics assembly also includes an optical element. The optical element includes a frame having a post. The optical element also includes a micro-optic mounted in the frame. The post is secured in a solid solder material disposed within the solder well in the cylindrical body.

In accordance with other aspects of the subject disclosure, a method is provided that includes melting solder within a solder well of a cylindrical mounting body in an optical bench of a micro-optics assembly. The method also includes inserting a post of a frame of an optical element into the melted solder within the solder well. The method also includes aligning a micro-optic mounted in the frame while the post is disposed in the melted solder in the solder well. The method also includes solidifying the solder to secure the aligned micro-optic to the optical bench.

In accordance with other aspects of the subject disclosure, an optical bench for a micro-optics assembly is provided, the optical bench including an opening and a cylindrical body press-fit in the opening. The cylindrical body includes a solder well at a first end. The cylindrical body also includes solder disposed in the solder well. The cylindrical body also includes a cavity at an opposing second end. The optical bench also includes a heating element disposed in the cavity and thermally coupled to the solder well.

It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory and are intended to provide further explanation of the subject technology as claimed. It is also to be understood that other aspects may be utilized and changes may be made without departing from the scope of the subject technology.

DETAILED DESCRIPTION

In accordance with various aspect of the disclosure, micro-optics assemblies, and assembly and reconfiguration methods for micro-optics assemblies, are provided. The systems and methods disclosed herein provide various improvements over conventional high-pitch tip/tilt mount optical systems, at least in part, because the adjustment mechanisms for the optics of a micro-optics assembly are taken out of the mechanical chain after optic mounting. In other words, the optic positioning tooling used for adjusting the optic positioning and alignment is not required to hold the optic in place for the duration of the life of the micro-optics assembly. Instead, an optical bench is provided which does not require the optic positioning tooling to retain the optic's alignment, and the optic positioning tooling can be removed from the micro-optics assembly after alignment of the optics. In this way, space, mass and complexity are reduced in the final, assembled micro-optics assembly, in comparison with conventional micro-optic systems.

Additionally, since the optic positioning tooling is not part of the final optic mounting, the size reduction of the optic elements themselves is not limited by the size constraint of the optic positioning tooling, but rather the size of the optic and optic mount itself. This allows micro-optics to be as small as, or smaller than, 2 mm in diameter (for example). These smaller optics can also be mounted closer together for higher fill factor densities. Higher fill factors benefit optical assemblies by reducing size as well as reducing round trip path length times, which can be particularly useful in systems in which the length of time required for a photon to traverse the optical path is desired to be small. As described in further detail hereinafter, the material combinations described herein for the micro-optics assembly are particularly advantageous for enabling the removal of the optic positioning tooling while allowing the micro-optics to retain the desired position and alignment in the absence of the optic positioning tooling.

FIG. 1illustrates a block diagram of an exemplary system having a micro-optics assembly. As shown inFIG. 1, system100includes micro-optics assembly101. Micro-optics assembly101includes optical bench102and optical elements108. Optical bench102includes one or more coupling elements104mounted therein for mechanically securing optical elements108to optical bench102in a desired alignment. As described in further detail hereinafter, coupling elements104, optical bench102, and portions of optical elements108may be formed from materials that have a common coefficient of thermal expansion so that changes in temperature of the micro-optics assembly do not alter the alignment of optical elements108.

Optical bench102also includes one or more electrical elements106. Each electrical element106may be associated with a corresponding coupling element104. Electrical elements106may be electrical heating elements.

Each optical element108may include an optic (e.g., a lens, a mirror, a grating, or the like) and a mounting frame. The mounting frame may include a structure for supporting the optic and a mounting post extending from the structure. Each electrical element106may include a heating element operable to melt solder within a solder well of a corresponding coupling element104. A mounting post of a corresponding optical element108may be inserted into the solder well.

Micro-optics assembly101may also include one or more light sources110such as laser light sources. Each laser light source may be mounted to optical bench102using one of coupling elements104in a manner similar to the mounting of optical elements108. In the example ofFIG. 2, micro-optics assembly101includes twelve optical elements108and six light sources110, which may be mounted within an area of optical bench102of, for example, less than one square inch. However, this is merely illustrative and more or less (e.g., twenty-five optical elements and light sources) can be mounted within one square inch of optical bench102in various implementations.

System100may be a standalone micro-optics assembly or may be a larger system in which micro-optics assembly101is included. For example, system100may be a frequency converter that incorporates a micro-optics assembly101in which pulsed laser light from one or more laser light sources is provided to one or more non-linear micro-optics of optical elements108to convert the frequency of the laser. As another example, system100may be a high power laser system that includes the frequency converter or a relatively larger system that incorporates a high power laser system. In these example systems, a short optical path length in the micro-optics assembly101may be desirable and may be provided by optical elements108and optical bench102that are free of alignment tooling.

System100may also be a relatively larger system such as an aircraft, a spacecraft, a satellite, a watercraft, or a land-based vehicle that incorporates micro-optics assembly101. In such systems, other components114may be provided such as mounting structures for micro-optics assembly101, propulsion components, or other components as would be understood by one skilled in the art. System100may also include communications circuitry112.

Communications circuitry112may include one or more antennas, processing circuitry, front-end circuitry, etc. for receiving and/or transmitting optical or other wired or wireless electronic communications for system100. Communications circuitry112may include receiver circuitry for receiving operational instructions for operating micro-optics assembly101(e.g., for operating light sources110). Communications circuitry112may include transmitter circuitry configured to transmit information regarding the status, operations, or other aspects of micro-optics assembly101.

Other components114may also include an enclosure for micro-optics assembly101. The enclosure and micro-optics assembly101may be arranged to form a resonant cavity having an optical path length (e.g., defined by optical elements108) that is an integer multiple of the light from one or more of light sources110.

Other components114may also include temporary components that are used for positioning and aligning optical elements108and/or light sources110on optical bench102. For example, the temporary components may include fine adjustment tooling that is external to the micro-optics assembly101for placing, positioning, and aligning each of optical elements108and/or light sources110on optical bench102. The temporary components may also include optic alignment measuring equipment that provides alignment data to the fine adjustment tooling during alignment operations. The optic alignment measuring equipment may obtain alignment information for each of optical elements108and/or light sources110during alignment operations based on light from light sources110and/or by capturing images or other data indicative of the position and alignment of optical elements108and/or light sources110. Other components114may include one or more processors and/or memory (e.g., non-transitory computer-readable media) storing instructions that, when executed by the one or more processors causes the fine adjustment tooling and the optic alignment measuring equipment to position and align one or more optical elements108and/or one or more light sources110on optical bench102. Other components114may include one or more processors and/or memory (e.g., non-transitory computer-readable media) storing instructions that, when executed by the one or more processors cause light sources110to operate to perform a function such as a frequency converter function for system100.

FIG. 2illustrates a perspective view of an exemplary implementation of micro-optics assembly101in accordance with some aspects. In the example ofFIG. 2, optical bench102of micro-optics assembly101includes multiple coupling elements104, each disposed in an opening in the optical bench. Each coupling element104includes an optical element108or a light source110mounted thereto. Optical elements108and light sources110are arranged to generate and guide light through the optical elements in a desired pattern. As shown, each of optical elements108and each of light sources110is mounted in a frame that is mechanically coupled to a corresponding coupling element104.

FIG. 2includes a cutaway portion in which cross-sectional views of two of coupling elements104are visible. As shown, coupling elements104may include a cylindrical body (sometimes referred to herein as a cylindrical mounting body). Electrical elements106(e.g., heating elements) may be mounted within a cavity in a corresponding cylindrical mounting body. Each cylindrical mounting body may be secured (e.g., by a press-fit) in a corresponding opening in optical bench102.

FIG. 3shows an enlarged view of a portion of optical bench102having a coupling element104. In the example ofFIG. 3, no optical element is shown so that cylindrical mounting body200and a solder well202in the cylindrical mounting body can be seen. As shown, an upper surface of cylindrical mounting body200may be mounted flush with the upper surface (e.g., the optic mount surface) of optical bench102.

FIG. 4shows cylindrical mounting body200separately from optical bench102. To install cylindrical mounting body200in optical bench102, cylindrical mounting body may be press fit into a corresponding opening in optical bench102.

FIG. 5shows an enlarged cross-sectional perspective view of a portion of micro-optics assembly101in which an optical element108is mounted to a cylindrical mounting body200that is disposed in an opening512of optical bench102. As shown inFIG. 5, optical element108may include a frame500. An optic such as micro-optic502(e.g., an optic having a diameter of less than 12 mm, less than 10 mm, less than 5 arm, less than 3 mm, or approximately 2 mm) is mounted in frame500(e.g., using adhesive504such as a high temperature ceramic epoxy). First and second posts506and510extend from opposing sides of frame500. Posts506and510may extend from frame500in a direction perpendicular to the optic light travel plane, which is generally parallel to the optic mount surface of optical bench102on which optical elements108and light sources110are mounted.

Post510is immersed in solder508disposed within solder well202of cylindrical mounting body200. Solder508may be in a liquid state (e.g., during alignment operations) or a solid state (e.g., after alignment has been completed and/or during operation of micro-optics assembly). In order to control the state of solder508, heating element514(e.g., a resistive heating element controllable by an electrical supply current) may be activated (e.g., to melt solder508) or deactivated (e.g., to solidify solder508). Heating element514is mounted in a cavity515in cylindrical mounting body200. As shown inFIG. 5, solder well202and solder508are axially separated from cavity515by a portion of the material of cylindrical mounting body200such that solder508is heated via heating of cylindrical mounting body200by heating element514. Cavity515may have an axial length within cylindrical mounting body200that is longer than the axial length of solder well202. Retainer516may be press fit into an opposing side of the opening in optical bench102in which cylindrical mounting body200is disposed to secure heating element514in cavity515.

Post506may be gripped and manipulated by one or more of other components114(e.g., fine adjustment tooling) to place post510into solder508and to rotate and otherwise position frame500to align micro-optic502as desired. Prior to release of post506by the fine adjustment tooling, heating element514may be deactivated to solidify solder508, thereby securing optical element108in an aligned position.

If it is desired to reposition optical element108(e.g., if micro-optic502is misaligned or if a different configuration of micro-optics502is desired), heating element514can be reactivated to re-melt solder508to allow realignment of optical element108. In this way, a reconfigurable micro-optics assembly may be provided.

Cylindrical mounting body200may be formed, for example, from copper or copper tungsten (CuW). The copper or CuW cylindrical mounting body may be electroplated in gold. Solder508may be formed from, for example, tin-silver-copper (SAC) or gold-tin (AuSn) solder. Frame500may be a titanium frame. The titanium frame may be coated (e.g., electroplated) with another metal such as gold to encourage wetting of solder508to post510. Optical bench102may be formed from, for example, titanium.

Various combinations of materials may be chosen such that optical bench102, cylindrical mounting body200, solder508, and frame500have a common or similar coefficient of thermal expansion (CTE). In this way, misalignment of optical elements108during temperature excursions for micro-optics assembly101can be reduced or prevented (e.g., to within an accuracy of less than 20 arcseconds), even over large temperature excursions in the range of, for example, −40 C to +70 C.

In one example, an SAC solder and a copper cylindrical mounting body may be provided. In another example, an AuSn solder and a CuW cylindrical mounting body may be provided. Although mounting body200is shown and described herein as being cylindrical in various examples, it should be appreciated that the outer surface of body200can have other shapes such as an elongate rectangular shape.

CuW mounting bodies200may provide an additional advantage over copper mounting bodies in that annealing the copper sleeve during heating of a copper sleeve to melt the solder can be prevented, thus providing a more reliable interference press fit within the opening in optical bench102.

FIG. 6depicts a flow diagram of an example process for assembling a micro-optics assembly such as micro-optics assembly101, according to aspects of the subject technology. For explanatory purposes, the example process ofFIG. 6is described herein with reference to the components ofFIGS. 1-5. Further for explanatory purposes, the blocks of the example process ofFIG. 6are described herein as occurring in series, or linearly. However, multiple blocks of the example process ofFIG. 6may occur in parallel. In addition, the blocks of the example process ofFIG. 6need not be performed in the order shown and/or one or more of the blocks of the example process ofFIG. 6need not be performed.

In the depicted example flow diagram, at block600, a heating element such as heating element514in a cylindrical mounting body such as cylindrical mounting body200in an optical bench such as optical bench102may be activated to melt solder such as solder508disposed in a solder well such as solder well202within the cylindrical mounting body. Activating the heating element may include providing electrical power to the heating element Activating the heating element may include activating the heating element to produce just enough heat within cylindrical mounting body200to melt the solder508in well202, the solder having been previously filled and wetted, opposite of the heater, in the solder well. Activating the heating element may include generating heat for the solder quickly and without overheating the solder.

At block602, a post such as post510on a frame such as frame500of an optical element such as optical element108may be provided (e.g., inserted) into the melted solder508in solder well202. Fine adjustment tooling mechanically coupled to an opposing post such as post506may be used to move frame500to insert the post into the solder. In this way, in accordance with some aspects, once the solder is liquid, micro-optic502bonded within the frame500(e.g., a gold plated titanium frame) is introduced into the micro-optics assembly and, using the external fine adjustment tooling to hold and manipulate the micro-optic frame assembly, the post in the titanium frame is plunged into the liquid solder, and the solder wets to the post due to its gold coating.

At block604, the external fine adjustment tooling may be operated to hold and manipulate optic frame500while measuring alignment of micro-optic502mounted in the frame using external optic alignment measuring equipment. For example, using optic alignment measurement techniques and measuring equipment external to assembly101to determine and/or track the position and alignment of the micro-optic, micro-optic502is moved and adjusted while post510is immersed in the liquid solder508.

At block606, heating element514may be deactivated to solidify solder508to secure aligned micro-optic502to optical bench102in an aligned position. In this way, once the position and alignment of micro-optic502if finalized, heater514is deactivated, and solder508freezes. Once solder508is fully cooled and solid, the external fine adjustment tooling releases post506of the micro-optic frame and the tooling is removed. If, after optic alignment is finalized, the user would like to adjust a previously aligned micro-optic, the heating element514associated with that micro-optic (e.g., mounted within the same cylindrical mounting body as the frame of that micro-optic) can be reactivated and the solder re-melted. Once the solder is re-melted, the micro-optic position and alignment can be manipulated again (e.g., using the operations of block604). When the re-alignment operations are complete, solder508can be refrozen with the micro-optic in its new alignment.

At block608, one or more light sources such as light sources110(e.g., laser light sources) for illuminating the secured aligned micro-optic can be provided. Providing the one or more light sources may include mounting each light source in a frame500having posts506and510and mounting the frame500with the light source therein to the optical bench using the operations of blocks600-606for the light source instead of the optical element. In this way, reconfigurable a micro-optic assembly can be provided.

At block610, the assembled reconfigurable micro-optics assembly (e.g., the optical bench with secured aligned optics and/or one or more light sources) may be provided in in an optical system such as system100ofFIG. 1.

The description of the subject technology is provided to enable any person skilled in the art to practice the various aspects described herein. While the subject technology has been particularly described with reference to the various figures and aspects, it should be understood that these are for illustration purposes only and should not be taken as limiting the scope of the subject technology.

There may be many other ways to implement the subject technology. Various functions and elements described herein may be partitioned differently from those shown without departing from the scope of the subject technology. Various modifications to these aspects will be readily apparent to those skilled in the art, and generic principles defined herein may be applied to other aspects. Thus, many changes and modifications may be made to the subject technology, by one having ordinary skill in the art, without departing from the scope of the subject technology.

It is understood that the specific order or hierarchy of steps in the processes disclosed is an illustration of exemplifying approaches. Based upon design preferences, it is understood that the specific order or hierarchy of steps in the processes may be rearranged. Some of the steps may be performed simultaneously.

It is noted that dimensional aspects (e.g., height, diameter, angular accuracy, fill factor) provided above are examples and that other values for the dimensions can be utilized in accordance with one or more implementations. Furthermore, the dimensional aspects provided above are generally nominal values. As would be appreciated by a person skilled in the art, each dimensional aspect, such as a diameter, has a tolerance associated with the dimensional aspect.