Laser grid structures for wireless high speed data transfers

Disclosed herein are various embodiments for high performance wireless data transfers. In an example embodiment, laser chips are used to support the data transfers using laser signals that encode the data to be transferred. The laser chip can be configured to (1) receive a digital signal and (2) responsive to the received digital signal, generate and emit a variable laser signal, wherein the laser chip comprises a laser-emitting epitaxial structure, wherein the laser-emitting epitaxial structure comprises a plurality of laser-emitting regions within a single mesa structure that generate the variable laser signal. Also disclosed are a number of embodiments for a photonics receiver that can receive and digitize the laser signals produced by the laser chips. Such technology can be used to wireless transfer large data sets such as lidar point clouds at high data rates.

INTRODUCTION

Wireless connectivity is becoming an important method for transferring data. However, it is believed that improvements are needed in this art. For example, there are many technical challenges with respect to wirelessly transferring large data files while maintaining high data transfer rates, particularly when transferring data from vehicles, such as autonomous vehicles (e.g., self-driving motor vehicles), to data centers as well as other applications that need large high speed file transfers.

A conventional approach to massive data retrieval (an example of which can include transfers of large sets of automotive data) may use a standard TCP/IP Ethernet network link with fiber optic connections.

Light detection and ranging (lidar) technology is often used in autonomous automobiles, where lidar sensors on the vehicle will generate extremely large data files in the form of lidar point clouds. These lidar point clouds can be 3D views of the images surrounding the vehicle. Typically, these views are taken 30× per second, which results in data storage needs for the vehicle that are quite extensive. For example, 20 terabytes (TB) may be required. Data storage units in the vehicle (typically located in the vehicle trunk) are used to store these large lidar point clouds. However, efficiently and effectively transferring these large point clouds out of vehicle storage and to a remote data center for analysis and/or further distribution is a challenging task for which improvements are needed.

As a solution to these problems in the art, the inventors disclose low-cost, highly efficient, and high-power semiconductor laser structures that can be used in a photonic emitter to optically transfer data at high data rates. An example of such a semiconductor laser structure can be a laser chip that includes a laser-emitting epitaxial structure, where the laser-emitting epitaxial structure includes a plurality of laser regions within a single mesa structure. These laser regions can be controllably activated to generate and emit variable laser signals that encode an input data signal. Such semiconductor laser structures can be arranged as a light grid array.

In an example embodiment involving data transfers from vehicles using such light grid arrays, data centers can receive the data from the vehicles (e.g, lidar point clouds) as it relates to the constantly changing stream of data that was the driver's (or virtual driver's) environment. The data centers can then organize, process, store, and distribute data back to other vehicles in the environment to enable those other vehicles to detect, identify, and react to their immediate environment. With such an environment, one-way high speed data transmissions between the data center and vehicle need to be timely and expedient; and the high speed data transfers that are made possible by the example embodiments described herein can make this possible while also simplifying the connection process of linking data storage with emitters, receivers, and data centers.

A data storage unit can be connected to such a photonics emitter via a fiber-channel connection. Accordingly, an optical signal can be used to represent a data set to be transferred. An optical data transceiver can receive this optical signal and convert it into a digital signal that represents the data set. This digital signal can be used to controllably activate the semiconductor laser structure so that the semiconductor laser structure generates and emits a variable laser signal that also represents the data set. This laser signal can be directed to a data center to achieve the data transfer. Such a data transfer can be performed significantly more quickly and efficiently because of the light grid technology discussed below that is capable of virtually unlimited data transfer rates.

Moreover, the laser signals can be heavily multiplexed if desired by a practitioner to further dramatically increase bandwidth. Thus, the photonics emitter can support multiple optical channels of incoming data and generate a multiplexed laser beam to transfer the data within those optical channels.

In an example embodiment, the photonics emitter can include a plurality of laser chips, where each laser chip is linked to data storage via a different fiber channel. Thus, multiple fiber channels can feed a given photonics emitter. As an example, each fiber channel linking data storage with the photonics emitter can provide a 16 Gbps optical signal to a different laser chip on the emitter. If 4 such fiber channels are linked to 4 laser chips, the 4 laser signals produced by the 4 laser chips can then be multiplexed together to create a combined laser beam that supports 64 Gbps of data communication. Further still, in an example embodiment, the different laser chips in the emitter can produce laser signals at different wavelengths relative to each other, and multiplexing can be achieved via techniques such as Coarse Wavelength Division Multiplexing (CWDM).

Further still, multiple multi-channel photonics emitters can be combined together to further increase bandwidth, for example using spatial multiplexing. As an example, five 4-channel photonics emitters could be included as part of a vehicle, each channel supports 16 Gbps, which results in the creation of 5 multiplexed laser beams, each supporting 64 Gbps, thereby yielding an expected total bandwidth of around 320 Gbps. As noted above, there may be a need to transfer 20 TB of data from a vehicle, and it is desirable to achieve such a transfer within 10 minutes. The expected 320 Gbps bandwidth that would be available from the deployment of five 4-channel photonics emitters (where each channel supports 16 Gbps) can satisfy such data transfer needs.

Also, because of the nature of the optical data transfer (where laser beams that encode data are used are routed to a data center), the data transfer can use higher efficiency storage protocols for the data rather than TCP/IP if desired by a practitioner. Instead, the storage protocols in the data center can be used for formatting the data being transferred, which allows a high speed connection or extension of the data center's powerful calculations capability. Thus, because the complex structuring required by TCP/IP networking can be avoided, less overhead is needed in the data being transferred, thereby yielding additional benefits.

As additional example embodiments, the inventors also disclose a number of innovations with respect to photonics receivers that can be used to receive and convert the laser signals from the photonics emitters into digital data for processing by data centers. For example, photonics receivers that work in coordination with the photonics emitters can be located in parking structures near small local data centers that serve as edge computing centers.

These and other features and advantages of the present invention will be described hereinafter to those having ordinary skill in the art.

DETAILED DESCRIPTION OF EXAMPLE EMBODIMENTS

FIG. 25shows an example embodiment of a photonics emitter2500that optically transfers data from data storage2520. A fiber channel2502can link data storage2520with photonics emitter2500via an optical data transceiver2506. A data set (such as a large data file, e.g., a lidar point cloud) can be propagated as an optical signal2504through the fiber channel2502. The optical data transceiver2506can then receive and convert this optical signal2504into a digital signal2508. This digital signal serves as a digital representation (e.g., 1s and 0s) of the data set.

This digital signal2508is then use to drive a laser chip2510in the photonics emitter2500. The laser chip2510thus produces and emits a variable laser signal2512that is responsive to the digital signal2508. As such, the variable laser signal2512also encodes the data set.

The laser chip2510can be a laser-emitting epitaxial structure having a plurality of laser regions within a single mesa structure, each laser region generating and producing a laser beam in response to the digital signal2508. Examples of devices that can be used as laser chip2510are disclosed and described in US Pat. App. Pub. 2017/0033535, the entire disclosure of which is incorporated herein by reference and a copy of which is included herewith as Appendix A.

Appendix A describes multi-conductive grid-forming laser structures, which in an example embodiment, can be embodied by a single unit of semiconductor lasers in a mesa structure, and their connections to a high speed electrical waveguide for high frequency operation. Additional examples of devices that can be used as laser chip2510are disclosed and described in the following U.S. patent applications, the entire disclosures of each of which are incorporated herein by reference: (1) U.S. patent application 62/456,476, filed Feb. 2, 2017, and entitled “Methods to Advance Light Grid Structures for Low-Cost Laser Sources”, (2) U.S. patent application 62/456,489, filed Feb. 2, 2017, and entitled “Fabrication of Light Grid Structures with Wafer Scale Processing”, (3) U.S. patent application 62/456,501, filed Feb. 2, 2017, and entitled “High Power Laser Grid Structure for Applications over Distance”, (4) U.S. patent application 62/456,518, filed Feb. 2, 2017, and entitled “Methods for Advancing High Brightness Diodes”, (5) U.S. patent application 62/459,061, filed Feb. 15, 2017, and entitled “Rigid Lasing Grid Structure Array Configured to Scan, Communicate, and Process Materials Using Deformable Light Fields” and (6) U.S. patent application Ser. No. 16/011,417, filed Jun. 18, 2018, and entitled “Graphene Lens Structures for Use with Light Engine and Grid Laser Structures”

Also, the laser chip2510can be arranged as an array of multiple laser-emitting epitaxial structures, each laser-emitting epitaxial structure having a single mesa structure, where the single mesa structure includes multiple isolated laser regions. In such an array, the laser chip2510may have multiple mesa structures, where each mesa structure includes multiple isolated laser regions. Such a laser grid structure can exhibit high numbers of laser emitters on a small chip.

FIG. 26shows an example embodiment of a multi-channel photonics emitter2500. In this example, the photonics emitter2500supports a plurality of optical channels. Each optical channel includes a laser chip2510and is fed by a digital signal2508from an upstream optical data transceiver2506. As such, the different laser chips2520produce different laser signals2512that are responsive to the respective digital signals2508that were applied to those laser chips2510. Each laser chip2510can produce laser signals of different wavelengths relative to each other.

Positioned optically downstream from the laser chips2510is an optical multiplexer2600. The optical multiplexer2600combines the laser signals2512from the different laser chips2510into a combined laser beam2602. This combined laser beam2602encodes data from the different optical channels and can be transmitted to a photonics receiver for receipt by a remote computer system such as a data center. Any of a number of techniques can be used to multiplex the laser signals2512. For example, Coarse Wavelength Division Multiplexing (CWDM) could be employed. As another example, Dense Wavelength Division Multiplexing (DWDM) could be employed. As yet another example, amplitude modulation could be employed.

Continuing with the example above where each optical data transceiver2506can be fed with an optical signal2504via a fiber channel2502that supports 16 Gbps bandwidth. In this example, where there are four optical channels in the photonics emitter2500, the resultant combined laser beam2602can support a 64 Gbps bandwidth. However, it should be understood that other data rates could be employed within the fiber channels2502. Further still, it should be understood that more or fewer optical channels can be used in the photonics emitter than the 4 optical channels shown byFIG. 26.

FIG. 27shows an example embodiment of a photonics receiver2700for use in coordination with the photonics emitter2500ofFIG. 26. Collector lens2710of the receiver2700can receive the incoming combined laser beam2602, and the receiver2700can convert the combined laser beam2602into digital data2708for processing by one or more processors within a data center. The receiver2700can include routing optics2702that route the combined laser beam2602to an optical demultiplexer2704. As an example, an array of optical filters that are positioned optically upstream from an array of photodetectors can serve as the optical demultiplexer. With such an arrangement, each optical filter can be a narrow band optical filter positioned over a corresponding photodetector, where the filters would only allow the correct wavelength signal to drive the photodetectors. The optical demultiplexer2704can demultiplex the combined laser beam2602back into its constituent laser signals2512of different wavelengths. Each of these demultiplexed laser signals2512can be applied to a different photodetector2706, where each photodetector2706converts its incident laser signal2512into the digital data2708.

Once again, while the example ofFIG. 27shows 4-channel receiver2700, it should be understood that the receiver2700can include more or fewer channels if desired by a practitioner.

The routing optics2702can employ any of number of different types of optical elements to route the combined laser beam2602to the optical demultiplexer2704. For example, one or more mirrors can be included in the optical path between the collector lens2710and the optical demultiplexer2704. Such mirror(s) can be used to re-direct the laser beam in desired directions to reach the optical multiplexer2704. Through such re-direction, the routing optics can accommodate any geometric challenges that may exist in a particular physical space for communicating light from lens2710to the optical demultiplexer2704(e.g., turning corners).

Such mirror(s) may take the form of a fixed mirror within the routing optics2702. However, in another example embodiment, the mirror(s) may take the form of micro-electro-mechanical systems (MEMS) mirrors. A MEMS mirror can be rotatable about an axis, and thus can be controllably cycled so that incident light on the MEMS mirror is directed to a desired destination. Thus, a drive signal for the MEMS mirror can be timed according to where each beam needs to go. The use of MEMS mirrors in this fashion can reduce latency through high rate constant cycling.

As another example of optical elements in the routing optics2702, one or more beam splitters can be included in the optical path between the collector lens2710and the optical demultiplexer2704. With a beam splitter, more complex routing options are available to a practitioner as the laser beam can be selectively split and moved in multiple directions if desired. For example, a beam splitter can be used to drain off a portion of the beam and send it to another location (which may be a blade, memory core, router, or switch inside the data center).

As yet another example of optical element in the routing optics2702, fiber channels can be used as a medium of transport if desired by a practitioner.

Also, the routing optics2702can be configured as a series of modular units that are connectable to each other. Through such modularity, complex geometries can be accommodated using a variety of standardized modular units. For example, some modular units may include mirror(s) that provide 90 degree turns. Accordingly, a series of modular units can be connected with each other to provide a physical path for the receiver2700that routes around any physical obstructions that may exist in the path to the data center computer system. Alignment connectors can be provided between the modular units to provide automated alignment for the optical signals passing through the modular units. Such alignment can be achieved by emitter and detector units placed in an injection molded slot which is perpendicular to the optical axis for an aligned beam. These holes or slots are engineered to position bulkhead-type connectors with high accuracy yielding a direct pre-positioned line-of-site connection. Examples of such modularity are shown in connection withFIGS. 28-29discussed below.

Also, it should be understood that similar routing optics could be provided in the path between the optical demultiplexer2704and photodetectors2706if desired by a practitioner.

FIG. 28shows an example data transfer system where a vehicle uses multiple multi-channel photonics emitters2500for optically transferring data to a photonics receiver2700that includes a modular snap in section2802. In this example, the vehicle includes various data storage units in the trunk. 16 Gbps fiber channels can link each of the trunk storage units with a 4-channel photonics emitter2500that is included as part of roof transmitter2800on the vehicle. In this example, the roof transmitter2800includes five 4-channel photonics emitters2500. As noted above, such an approach means that the roof transmitter2800is expected to support a bandwidth of around 320 Gbps out of the trunk data storage.

The receiver2700can be positioned in a parking structure for the vehicle, and each 64 Gbps laser beam from the roof transmitter2700can be collimated to pre-aligned mirrors (see, e.g. mirror2804) which guide each beam's data in a spatially multiplexed configuration.

FIG. 29shows the spatially multiplexed beams' paths being routed in and through additional modular sections2804of the receiver2700within a data center. As shown, each modular section2804includes mirrors that route the beams in new directions, and in the aggregate the modular sections2804route the beams to optical multiplexers (see2704inFIG. 29). Each demultiplexer2704can de-multiplex the 4 wavelengths for distribution to individual photodetectors for different processing cores.

FIG. 30shows an example of how a data transfer system such as that shown byFIGS. 28-29can be deployed in a parking structure. In this example, the various vehicles include roof transmitters2800and transmit high data rate laser beams into receivers2700that are positioned overhead in the parking structure. The routing optics2702in the receivers2700then route the laser beams to desired destinations in the data center as discussed above.

FIG. 31shows a modular receiver2700where access panels or lids can be included as part of the structure to provide access points3100into the structure. The access points can show where beams are positioned to specific mirror locations which can be adjusted through the access points3100. The modular units2804can be constructed such that the tolerances of the beams' locations falls within the mechanical specifications of the modular units. Such an arrangement can allow for rapid construction of a receiver2700in data center operations without beam alignment.

While various examples discussed above describe use of the innovative data transfer system with automobiles and parking structures, it should be understood that this data transfer technology can be used in many applications other than automobiles and parking structures. For example, the modular receiver2700can be used with tunnels, and it can also distribute beams from vehicles such as planes or trains.Furthermore, in an example embodiment, the photonics emitters and receivers described herein can be deployed in a miniaturized facility that is optimized for data storage and delivery by using a multiple wavelength wireless optical backbone co-joined to a wireless optical backhaul that is configured to interface with multiple similar embodiments which form a localized data center based on a wireless mesh network configuration for redundancy and verification. The connectivity of the optical backhaul is wireless using the light grid/light engine beams described above and below using low coherent wavelength span specific arrays of multiplexed channels; for example at 10 Gbps. Although the inventors expects that 50 Gbps per channel is possible. The configuration uses a distribution node for multiple links to other similar embodiments which act as a wirelessly-connected data center where switching is minimized because of the beams or channels of information that are distributed at nodes with multiplexed and semi-transparent beam separation and routing. These functions create a unique capability to enhance information exchange in rural or non-rural communities. The purpose or goal would be a data center for storage, retrieval of local traffic while minimizing outside connection bandwidth necessary for full functionality. Each embodiment can be a building block of a localized network where the majority of web traffic is directed to a local infrastructure composed of single or multiple miniaturized storage and microprocessors that are attached to the nodes or linked mesh network. Units of processing power or memory functions of the data center can then be leased or purchased by customers.

For example,FIG. 32Ashows an example data center3200where a plurality of wireless optical nodes3202are arranged to send and receive optical data signals to and from external sources. The optical signals received by the nodes3202can be delivered as a multiplexed laser beam3204to a plurality of processing units3206(e.g., server blades) that are resident in the data center3200. This mode of signal processing can employ the techniques described above for the photonics receiver2700. The optical signals sent by the nodes3202can also be transmitted as a multiplexed laser beam to remote destinations. This mode of signal processing can employ the techniques described above for the photonics emitters2500and optical data transceiver2506.

The data center3200can also include a housing3208in which the server blades and optical routing components are located. The data center3202can also include a cooling fan3210to help avoid overheating. Further still, solar cells3214can be included as part of the data center to facilitate an ability to operate without necessarily needing access to conventional wall/outlet power. Furthermore, in the example ofFIG. 32A, the data center3200can also function as a lighting source (e.g., street light) via LEDs3212or the like, where a trunk or pole for the light source is used to house server blades, and where extensions from the top of the trunk/pole are used to hang LEDs3212from (with the top of the data center having solar cells3214positioned thereon to collect sunlight). However, it should be understood that the data center3200need not necessarily also be deployed as a street light or other light source.

FIG. 32Bshows a zoomed-in, cross-sectional view of the trunk/pole portion ofFIG. 32A. An optical backbone running down the trunk/pole can carry the multiplexed laser beam3204, and beam splitters3220can tap into this multiplexed laser beam3204are various points along the optical backbone, as shown byFIG. 32B. These beam splitters can selectively demultiplex signals3222from the multiplexed laser beam3204for delivery to particular server blades3206for processing.

FIG. 32Cshows an example embodiment of the wireless optical nodes3202. The nodes3202can be arranged as a plurality of wireless optical transceivers3230that are aimed to send and receive optical data to/from different directions. The optical signal received by each transceiver3230can be multiplexed to form combined beam3204. The transceivers3230can also include photonics emitters2500and optical data transceivers2506as discussed above in relation toFIGS. 25 and 26to multiplex data signals from different server blades3206for combination and transmission from the nodes3202. The wireless optical transceivers3230can be located within a housing3232that is transparent to incident light at the wavelengths of interest (e.g., transparent to IR).

FIG. 32Dshows another example of a data center3200where no lighting functions are provided. In this example, the wireless optical nodes3202are positioned atop a base that is housed in a material using an injection-molded pattern or the like.

A number of the data centers3200can be geographically dispersed but within optical range of at least one of the other data centers3200so that a wireless mesh network can be formed for data transfers within an area. Accordingly, the transceivers3230within the nodes3202of a given data center3200can be aimed at other transceivers3230within other nodes3202/data centers3200in the mesh network.

Accordingly, the innovative data transfer technology disclosed herein can be used to support the wireless transfer of large data files in any of number of applications. By leveraging the light grid technology described above and below which can exhibit high-speeds (in excess of 1 GHz on/off rates) and high-power outputs from VCSEL semiconductor laser arrays, this innovative data transfer technology provides higher yields than conventional VCSEL arrays due to a unique and specific architectural design improvement. The laser chips used in an emitter can use a simplified manufacturing design and process to achieve excellent performance for speed and power from an all-semiconductor laser chip which uses wafer-scale processes to eliminate complex assembly tasks. The results achieved are miniaturization, reduction in cost, and an increase in the flexibility of beam characteristics using the manufacturing process instead of expensive and complex alignment with external micro-lens/mirror arrays. As such, the present technology will advance automated fabrication of high-beam-quality, high-power, short-coherence-length semiconductor laser arrays that could be used as high speed wireless data transmission for autonomous vehicle downloads.

While the present invention has been described above in relation to example embodiments, various modifications may be made thereto that still fall within the invention's scope, as would be recognized by those of ordinary skill in the art. Such modifications to the invention will be recognizable upon review of the teachings herein. As such, the full scope of the present invention is to be defined solely by the appended claims and their legal equivalents.

Appendix A—US Pat App Pub 2017/0033535

Laser arrays are becoming important in the field of communications, light detection and ranging (LiDaR), and materials processing because of their higher operational optical power and high frequency operation as compared to single lasers, fiber lasers, diode pumped solid state (DPSS) lasers, and light emitting diodes (LEDs).

Laser arrays are commonly used in printing and communications, but in configurations which have a single separate connection to each laser device in the array for parallel communication where each laser could have a separate signal because it had a separate contact from the other devices in the array.

When array elements were tied together and driven with a single signal, the structures had too much capacitance or inductance. This high capacitance/inductance characteristic slowed the frequency response for the laser array down, thereby making such laser arrays slower as they added more elements. This is evidenced in the referenced works by Yoshikawa et al., “High Power VCSEL Devices for Free Space Optical Communications”, Proc. of Electronic Components and Technology Conference, 2005, pp. 1353-58 Vol. 2, and U.S. Pat. No. 5,978,408.

High speed laser arrays based on multi-mesa structures are described in the inventor's previous work, US Pat App. Pub. 2011/0176567. US Pat App. Pub. 2011/0176567 describes a multi-mesa array of semiconductor lasers and their connections to a high speed electrical waveguide for high frequency operation. However, the multi-mesa structures described in US Pat App. Pub. 2011/0176567 suffers from a number of shortcomings.

One problem with mesa structures as described in US Pat App. Pub. 2011/0176567 is they are typically brittle. This is a problem if there is any mechanical procedure to bond to or touch the laser after the mesa is formed. The mesas structures can be as small as 5 to 10 microns in diameter and consist of an extremely fragile material such as GaAs or AlGas, or other similar crystalline materials. These mesas must be bonded after processing and pressure is applied under heat so that the submount and the tops of the laser mesas are bonded electrically with solder. When bonding an array of back emitting devices a typical failure mechanism at bonding is a cracked mesa which renders the laser useless and can cause a rejection of the entire device. If there are 30 lasers on the chip and after bonding2are broken, those 2 devices will not light up. The testing still must be done causing an expensive process to remove failures.

Another problem is that the multi-mesa structure yields relatively low lasing power as a function of chip real estate because of spacing requirements for the multiple mesas that are present on the laser chip.

Another problem with the multiple mesa arrays produced by mesa isolation is that the lasers are separated by a distance which limits the overall size of the array due to frequency response-dependent design parameters that prefer shorter distance for a signal to travel across a contact pad. Later, arrays were used with elements which add in power such as the multi Vertical Cavity Surface Emitting Laser (VCSEL) arrays which were used for infrared (IR) illumination. However these IR sources did not support high frequency operation, so their pulse width was limited to illumination instead of LIDAR, which needs fast pulse widths.

In an effort to satisfy needs in the art for stronger and more powerful high speed laser arrays, the inventor discloses a number of inventive embodiments herein. For example, embodiments of the invention described below incorporate a high frequency electrical waveguide to connect lasers of the array together while reducing capacitance by forming the signal pad on the substrate which employs the electrical waveguide. Embodiments of the invention also comprise the use of multi-conductive current confinement techniques in a single structure to produce multiple areas that are conducting compared to non-conducting part of the structures. The conducting parts form lasing areas or grids of lasing forming lasers without etching around the entire structure of the lasing point. Unlike the design described in the above-referenced U.S. Pat. No. 5,978,408, embodiments of the invention disclosed herein are designed and processed so that the laser array is integrated with a high speed electrical waveguide to enable high frequency operation. Embodiments of the present invention support new and unique opportunities in the design of a high power high speed light sources by exhibiting both high frequency operation and a rigid structure, thus enhancing performance and reliability over other designs known in the art.

In an example embodiment disclosed herein, a unique structure processed from a Vertical Cavity Surface Emitting Laser (VCSEL) epitaxial material forms a grid of laser points from a single rigid structure which is conducive to high speed operation by reducing capacitance, increasing structural integrity, and decreasing the fill factor as compared to the typical mesa structures formed in VCSEL arrays such as those mentioned in US Pat App. Pub. 2011/0176567. It should be understood that the VCSEL embodiment is only an example, and such a design can work with other laser types, such as Resonant Cavity Light Emitting Diodes (RCLEDs), LEDs, or Vertical Extended (or External) Cavity Surface Emitting Lasers (VECSELs).

The single contiguous structure described herein forms areas of electrical isolation of apertures using implanting of ions or areas of nonconductive oxidation through microstructures or holes while keeping the structural integrity of the material that is typically etched away. The formation of the new structure also allows a high speed signal to be distributed between the different isolated laser conduction points or grid. All of the P-contact areas of the laser grid can be connected in parallel to the signal portion of a ground-signal-ground (GSG) integrated electrical waveguide. The signal or current being switched on and off in the waveguide is distributed between all of the conductive paths which form lasers. It should be understood that other types of electrical waveguides could be used such as a micro-strip waveguide.

The single contiguous structure has other benefits such as a larger base for heat distribution within a larger plating structure. The lasing grid is closer together than the array structures to each other. The farther the lasers are apart the slower the frequency response or the speed which limits the ultimate bandwidth of the device due to the distance the signal must travel to every single point in an array.

Accordingly, examples of advantages that arise from embodiments of the invention include:

1. Rigid structure has a higher reliability in the chip bonding process

2. Rigid structure has a higher fill factor possibility

3. Rigid structure has higher reliability metal contacts

4. Rigid structure is simpler to process

5. Rigid structure has shorter distance between contacts enabling higher frequency high power beams

6. Rigid structure is a better surface topology for a single lens or lens array to be attached

7. Rigid mesa structure produces another area for leads and contacts which offer separation from potentials lowering capacitance.

8. Rigid structures allow higher integration with sub mounts because of the 3D nature of the contacts.

Furthermore, with an example embodiment, a laser grid is formed by more than one lasing area enabled by confining the current to isolated regions in the structure where conductivity exists as compared to the nonconductive ion implanted areas. The conductive and nonconductive areas form a grid of light which has a single metal contact on the single solid structure for the active Positive contact and a single N Contact on the surrounding ground structure which is shorted to the N contact area at the bottom of the trench isolating the two areas. By way of example,FIG. 7Cshows how an opening in the frame would help increase the speed.

These P and N contacts are then bonded to a high speed electrical contact The 2 substrate and laser chips are aligned by a bonder then heat and pressure are applied to bond the solder that has been deposited on one chip or the other. The high speed is enabled because the p pad is separated from the n wafer ground by plating and solder heights but mostly by removing it off the laser substrate and placing it on an electrical waveguide substrate. The physical separations dramatically reduces capacitance increasing the frequency response which is limited by the capacitance of the circuit. This enables the lasing grid to achieve high frequency operation.

A single lens formed on the back of the substrate or a single Lens attached or bonded to the back of the grid structure could direct each lasing point from a convergence point or to a convergence point. This is ideal in collimating the beam output as if it were from a single source.

These and other features and advantages of the present invention will be described hereinafter to those having ordinary skill in the art.

Embodiment 1 for US Pat App Pub 2017/0033535—Top-Emitting Implant

FIG. 1shows an example of a first embodiment of the invention. In this example, a single solid structure is isolated from a surrounding ground with an etch, and where the single solid structure has within it ion implants. The ion implants create areas of the semiconductor material that are non-conductive, and these areas of non-conductivity force current flow through the lasing areas2. Thus, the ion implants form a laser grid of multiple lasing areas2where current is confined to isolated regions in the structure where conductivity exists as compared to the nonconductive ion-implanted areas. The conductive and nonconductive areas form a grid of light which has a single metal contact on the single solid structure for the active positive (P) contact and a single negative (N) contact on the surrounding ground structure which is shorted to the N contact area at the bottom of the trench isolating the two areas or to negative metal on the surrounding ground structure which is shorted to the N contact area at the bottom of the trench isolating the two areas (as in, for example,FIG. 7C(see reference numbers781and782). These P and N contacts are then bonded to a high speed electrical contact, thereby enabling the lasing grid to achieve high frequency operation.

WhileFIG. 1shows the lasing areas2arranged in a grid pattern, it should be understood that many shapes and patterns of lasing areas2could be formed. This allows many forms of structures with shapes/patterns of lasing areas2such as a honeycomb structure pattern (see, for example,FIG. 23which illustrates another pattern which is one of many allowing different laser shapes or patterns; there are many patterns that can be used for etching or implanting to leave conductive areas41for lasers in a single mesa structure versus non-conductive areas42) and other structure patterns which are more rigid while improving bonding. Heat removal can still be accomplished by depositing materials with high thermal conductivity materials in the holes that are etched into the single mesa structure to produce the multiple lasers (see, e.g., holes7005inFIG. 7) which are closer to the junctions. Examples of additional structure patterns can include arrangements like squares or circles on lines, etc.

FIG. 1shows a top view of the epitaxial side of a laser chip. A single laser-emitting epitaxial structure1has an ion-implanted area, all except the lasing areas2(which are shown as disks inFIG. 1) where the ion implant was masked.FIG. 1thus represents the chip after implant, and etch. Relative to the prior design of US Pat App Pub 2011/0176567 which has multiple epitaxial mesas with each mesa corresponding to a single lasing region, the design ofFIG. 1shows a single contiguous structure1that does not have multiple mesas and can instead be characterized as a single mesa, where this single mesa includes multiple lasing regions2. The illustration ofFIG. 1is meant to show the single mesa structure and not the electrical contacts. This structure1could be either bottom emitting or top emitting depending on the design and reflectance on the N mirror as compared to the P mirror.

1Single Active Mesa Structure which will produce multiple lasingpoints2Areas where implant is masked so that implant does not affectepitaxial region under mask.3Etched isolation trench separating the Single Active Mesa Structureand the Single Ground Structure4Single Ground Structure

FIG. 2is a cutaway view of the laser chip shown byFIG. 1, where the single active mesa structure1shown byFIG. 1is numbered as11inFIG. 2and where the masked implant areas2shown byFIG. 1are numbered as12inFIG. 2.FIG. 2represents the chip after implant, and etch but no top metal. Etched region13isolates the single mesa structure12from the “frame” or N mesa14(where the single ground structure4fromFIG. 1is shown as the frame/N mesa14inFIG. 2).FIG. 2shows:

11Implanted area of Single Active Mesa Structure isolating multiplelasing points12Areas of the Epitaxy Masked from Implant which will produce lasing13Etched isolation trench separating the Single Active Mesa Structure11 and the Single Ground Structure 1414Single Ground Structure15Quantum wells between the top P mirror and the bottom N mirror -this is an active region where Photons are emitted16N mirror which has N contact layer or highly doped layers for Nmetal electrical contact location17Laser substrate

FIG. 3is a perspective view of the chip shown byFIGS. 1 and 2. The implanted region is invisible. The metal contacts are not shown. This illustration is to show the topology of the single mesa etch, which can be used for either top-emitting or bottom-emitting implanted devices. The process of implant can take place before or after top metal or etch.

FIG. 4shows a top view of the epitaxial side of an example top emitting VCSEL grid structure. The view is through a square hole in the top electrical waveguide which is bonded by a solder process to the laser chip. The isolation etched region is hidden in this view by the electrical waveguide. The round disks on this illustration are the holes in the top metal contact or plated metal contact region over the single solid mesa structure.FIG. 4shows:

41Hole in substrate with waveguide underneath42Holes in the top P metal so laser beams can emit through43Top of waveguide substrate44Top spreading metal on laser chip

FIG. 5illustrates a cutaway view of the bonded electrical waveguide and laser chip shown byFIG. 4. The signal contact for the electrical waveguide is opened to allow the beams to propagate through the opening. Another option of this embodiment would be to have a transparent or transmitting substrate material for the waveguide instead of a hole for the lasers to propagate through. A transparent material such as CVD (Chemical Vapor Deposited) diamond or sapphire or glass could be an example of that material. This figure shows the embodiment with a substrate such as AlNi which is opaque and thus needs a hole or opening. Notice the isolation region is separating the single mesa structure from the single mesa ground or structure or “frame” structure which is shorted to ground.

These P and N contacts are bonded to a high speed electrical contact (see alsoFIG. 7B, reference numbers751through754). The ground-signal-ground (GSG) electrical waveguide substrate and laser chips are aligned (seeFIG. 14B) so that the negative mesa is bonded to the negative part of the waveguide and the positive active areas which lase are aligned to the signal pad. This alignment is defined by a bonder, then heat and pressure are applied to bond the solder that has been deposited on one chip or the other (seeFIG. 15) The high speed nature of this contact arises because the p pad is separated from the n wafer ground by plating and solder heights but mostly by removing it off the laser substrate and placing it on an electrical waveguide substrate. The physical separations dramatically reduce capacitance, thereby increasing the frequency response (where the frequency response is limited by the capacitance of the circuit) and yielding high frequency operation for the lasing grid.

In an example embodiment, for high speed operation, the surface connects to the electrical contact at the bottom of epi design, which is accomplished through the isolation trench (see, for example,FIG. 7Areference number702) surrounding the single structure (see, for example,FIG. 7A(reference number717)). This structure is not based on mesa topology but is simply shorted to the electrical region of the N contact metal (seeFIG. 7A(reference number703)) through the metal plating (such as inFIG. 7Creference number782). This is not a built up structure or raised structure as described in US Pat App. Pub. 2011/0176567 but rather uses the chip surface and the epi material to be a surface for bonding, which also makes the device much more stable and robust at bonding.

Returning toFIG. 5, the GSG Signal Pad51has Solder52electrical connecting the P Contact Metal on the top of the Active Single Mesa Structure. This allows the signal or current to be injected into the metal contact structure with holes in it for laser propagation and then the current flows through the non-implanted regions of the epitaxial structures forcing current to be confined to just those defined regions. The top P mirror region has a slightly lower reflectance than the bottom N mirror allowing the light to emit from the top of the epitaxial structure. The current flows on through the quantum wells which produce the light and heat in there junction, and into the n mirror where it proceeds to the N contact region in or near the n mirror. The current would then proceed up the shorted frame structure which is bonded and in electrical contact to the ground portion of the GSG electrical waveguide. This structure which utilizes top emitting design can be used for lower wavelength output designs which are lower than the transmission cutoff of the GaAs or laser substrate material. Back emitting structures can typically only be designed for wavelengths above ˜905 nm. This top emitting structure could be used with ˜850 nm or lower to the limits of the epitaxial material set.

A single solid structure isolated from a surrounding ground with an etch where the single solid structure has within it ion implants; the implants are invisible but cause the semiconductor material to be nonconductive because of the crystal damage it causes. In order to make an implanted device you must mask the areas that are to be protected from the damage first.

Small mesas are formed with photoresist positioned by a photolithographic process which protects the epitaxial material from damage then is washed off after the implant takes place. The implant happens in an ion implant machine which accelerates ions down a tube and you put the wafer in front of the stream of ions.

Implanted ions can create areas of the semiconductor material that are non-conductive. These areas of non-conductive material will force the current flow through the lase areas. These non-conductive areas can also be created by etching a pattern similar toFIG. 1and oxidizing the single structure as described below in connection with Embodiment 2.FIG. 5shows:

50Non Conducting Electrical Waveguide Substrate51Signal metal of electrical waveguide52Solder metal for bonding electrical waveguide to laser chip53Plated Metal shorted to P Contact Layer and electrically connected toSignal pad of GSG electrical waveguide54P Output Mirror-Diffractive Bragg Reflector55Active Region-Quantum Wells56N Mirror where low resistance contact Layer is located57Plated Metal shorting or in electrical contact with N Contact layerand to Ground Mesas58Solder in Electrical contact with Ground pad of electrical high speedwaveguide and in electrical contact with Grounded Mesa structure59Area on Plated metal connected to P Metal on single mesa structurefor contacting signal pad on high speed electrical waveguide

FIG. 24shows a comparative view of different current flows as between an embodiment such as Embodiment 1 and the design taught by US Pat App. Pub. 2011/0176567. With U.S. Pat App. Pub. 2011/0176567, each mesa is surrounded by an N metal contact area. This takes precious space or real estate on the chip as the processing to define those footstep metal n contacts around each mesa require photolithography which limits how closely you can space the mesas together. These limits lead to a lower power output per unit area than the new method. Therefore the goal of this old apparatus was an array for highest power and speed yet did not take into account the vast improvement in power/area which would also be an improvement in the ultimate goal of highest Power with the highest Speed. Also, this old method's N contact had to be large because of the structural limitations from the old method has been removed with the new single structure.

With the new design described herein, a single structure has several lasers on it and only one contact around that single structure. The new structure reduces that N metal area to the outside of the structure making the area per light element much smaller. This involves a large N contact layer calculated to carry the current load of the single structure. The higher current flow from the single contact can be realized through thicker metal and or thicker N contact region.

Embodiment 2 for US Pat App Pub 2017/0033535—Bottom-Emitting Implant

FIG. 6illustrates a cutaway view of an example of a second embodiment, where the second embodiment is a bottom-emitting device with implanted regions for current confinement. The GSG electrical waveguide can be seen solder bonded to the frame-ground structure and the active single laser mesa structure.FIG. 6shows:

601Electrical Waveguide Substrate602Ground Contact and Signal Contact in that order of GSGElectrical Waveguide603Solder-Bonding GSG Waveguide to Laser Chip604Plating Metal electrically connecting Signal pad of ElectricalWaveguide to Lasers P contact605P contact Metal606Implanted Region that has been rendered non conductive607P mirror608Active region (quantum wells)609N Mirror610Conducting Layers in N Mirror where Implant has not reached611Laser Beams Propagating through Laser Substrate612Plating Metal shorted to N contact region613Frame Area Shorted to N Contact region614Solder electrically contacting N contact on Laser to Groundon Electrical Waveguide615Etched region isolating large single mesa from Ground Frame

Process for Embodiments 1 and 2 of US Pat App Pub 2017/0033535

An example embodiment of the process steps to create the single structure for embodiments 1 and 2 with implant current confinement can be as follows.Step 1. Use photolithography to mask areas which will not have P Metal deposited.Step 2. Deposit P Metal (typically TiPtAu ˜2000 A)Step 3. Photolithography lift off and wafer cleaning. O2 descum or ash all organics off wafer.Step 4. Dielectric deposit (typically SiNx ˜<1000 A) used as an etch maskStep 5. Photolithographic masking using either photoresist or metal deposited in areas to protect the epi material from being damaged from the implant which makes the unprotected regions non-conductive through ion bombardment. This step can be performed later in the process but may be more difficult due to more varied topology.Step 6. Implant—Those skilled in the art of calculating the implant doses will determine the dose and species of implant needed to disrupt the materials structures to the depth which will isolate the p regions and the quantum wells from each other—Step 7 Cleaning this photolithography is difficult due to the implant and a deposition of metal over the photolithography such as plating could help to make it easier to clean off the resist.Step 8. Use photolithography to mask areas of dielectric which will not be etched. This is the unique part which is the design of the mask which creates a large isolated structure down implants within that structure define where current cannot flow.Step 9. Use plasma etch to etch through dielectric (typically Fl based etchant) can use wet etch such as BOE (buffered oxide etch).Step 10. Etch pattern into Laser or Light Emitting Diode Epitaxial material. Stop on Substrate or doped electrical contact layer. This isolates a single large structure from the N shorted regions around the chipStep 11. Clean off mask. O2 descum or ash all organics off wafer.Step 12. Use photolithography to mask areas which will not have N Metal deposited.Step 13. Deposit N Metal (Typically GeAu/Ni/Au eutectic composition of 80% Au/20% Ge by atomic weight. Total thickness of AuGe layer ˜3000 A or more with ˜200 A Ni or more of other diffusion barrier metal and ˜5000 A of Au or more This is also unique hear where the n metal is deposited in the n contact etched region and also up and over the N contact structure shorting the structure to the n-contact.Step 14. Clean off mask (typically called lift off). O2 descum or ash all organics off wafer.Step 15. Dielectric deposit (typically SiNx ˜2000 A) used as a non-conductive isolation barrierStep 16. Use photolithography to mask areas of dielectric which will not be etched.Step 17. Use plasma etch to etch through dielectric (typically Fl based etchant) can use wet etch such as BOE (buffered oxide etch).Step 18. Clean off mask. O2 descum or ash all organics off wafer.Step 19. Use photolithography to mask areas which will not have Plated Metal deposited.Step 20. Plate areas with ˜4-5 um of Metal (typically Au) or Cu if diffusion barrier can be deposited first.Step 21. Use photolithography to mask areas which will not have Solder deposited.Step 22. Deposit Solder Metal (Typically AuSn/Au eutectic composition of 80% Au/20% Sn by atomic weight. Total thickness of AuSn layer ˜40000 A (4 microns) or more with ˜500 A Au on top to stop any oxidation of Sn. This layer can be patterned and deposited on the submount with electrical waveguide which is bonded to the laser grid.

Embodiment 3 for US Pat App Pub 2017/0033535—Top-Emitting Oxidation

In a third embodiment, oxidation rather than ion implantation is used to create the grid of top-emitting lasing regions within the single structure. For example, a patterned etch can isolate conductive paths in a single structure, creating a grid of light sources. This structure exhibits multiple laser emission points from the single structure. The lasing structure is isolated with an etched region from the ground contact that forms the outside perimeter of the chip. This structure for Embodiment 3 is top emitting. The conductive areas of the grid are where light will be emitted. The positive electrical contact can be a grid with openings where the light is emitted.

The epitaxial material of the laser wafer can be a VCSEL design, and most VCSELs are top emitting. The distribution of the signal using a p type waveguide pad is typically on the laser wafer, but it should be understood that in an oxidated single structure embodiment that has a back emitting design, the waveguide can be on a separate substrate that is separated from the laser n material or layer.

FIG. 7, which shows an example of Embodiment 3, illustrates an example pattern etched into a wafer to create a single structure which allows multiple point lasing. The single structure of an embodiment such as that shown byFIG. 7is much more rigid than the thin columns made of fragile crystal material as taught by US Pat App. Pub. 2011/0176567. Also, as explained with respect to an embodiment discussed above, it should be understood that pattern of lasing areas other than that shown byFIG. 7may be employed if desired by a practitioner.

InFIG. 7, the diagonally striped areas are preferably etched down to create the patterned single mesa structure in the middle of the isolation trench. All diagonally striped areas are preferably etched down to the bottom N electrically conductive layer705inFIG. 7Aor typically the larger isolation trench will be etched to the electrical contact buried in the epitaxial design, while the smaller patterned etch areas must go deeper than the active region which isolates the lasing points. The patterned structure in the middle of the isolation trench is a single structure with “shaped” holes etched into it.

The holes in the large single mesa are large in this case. These holes allow the oxidation process environment to oxidize the layers in the epitaxial region. The oxide layer or layers has high aluminum content and forms AlO2that grows laterally through the layer until taken out of the oxidation process. White areas are the surface of the chip, dotted lines are where oxidation limits current flow to unoxidized areas only. The holes in the large single mesa are large in this case. These holes allow the oxidation process environment to oxidize the layers in the epitaxial region.

The oxidation layer can be formed by using a high Al content layer in the epi design structure which is buried below the surface. The etched areas expose that layer which is then placed in an oxidation chamber allowing the exposed layer to oxidize inward, where AlO2grows laterally through the layer until taken out of the oxidation process. As the length of the oxidation grows in that thin layer, it isolates or closes off the current paths with a dielectric material of AlO2that is formed during the oxidation process. If the areas7005are etched, then the oxidation will continue to grow until only areas7008are conductive and the area or part of the epitaxial layers which conduct the current through that section. Electrically conductive areas allow current flow through the quantum wells (seeFIG. 7Areference number707) and produce lasing as the light is trapped in the cavity between the p mirror709and N mirror706.

The oxidation length can be seen inFIG. 7as dotted lines, all about the same distance from any one exposed edge or holes in the large single structure that has holes formed in it.FIG. 7also shows the large single mesa ground structure. Three views of cross sections are illustrated to identify whereFIGS. 7A, 7B, and 7Care located. Note7B which clearly shows through this cross section that the mesa in the center is a single structure.

7001Frame (Single Shorted Mesa) for Electrical Contact to Groundof Electrical Waveguide7002Etched region isolating large single mesa from Ground Frame7003Single Mesa Structure with Etched Holes7004Indents in Edges to keep edges of Single Mesa Structure Oxidizedand Non Conductive7005Etched Hole in Single Mesa Structure7006Oxidation Pattern around any Etched Edges7007Overlapped Oxidized Areas not allowing Current Flow7008Laser Aperture where Current Flows freely (same as 761 inFIG. 7B)7009Gap in Shorted Mesa Structure to Reduce Capacitance fromGround to Signal Pad on Electrical Waveguide

FIGS. 7A,7A2and7B are side views of the exampleFIG. 7embodiment.

FIG.7A2shows the etched holes727that allow the oxidation731to form, which confines the current into region761ofFIG. 7B, for formation of laser beams763.

Reference number706inFIG. 7Ais a p mirror diffractive Bragg reflector (DBR) which has one or more layers in it with very high aluminum content708which when exposed to hot damp conditions oxidizes708confining the current to the areas761shown byFIG. 7B, which are where the laser beams come out. The N mirror DBR709has a conductive layer705to take the current flow out through the N metal ohmic contact703to the plating782(seeFIG. 7C) which goes up and over the single ground mesa structure718(seeFIG. 7A) to the solder717and electrically connecting to the N plating on the GSG waveguide716and into the N contact715of the waveguide.

Current confinement is a major part of a semiconductor laser. The concept is to force the current flow away from the edges of the structure so there is not an issue with current flowing near rough surface states that may exist from the etch. The current flow is also ideally concentrated to create lasing by increasing the current density in the material The current confinement occurs either by oxidation through allowing the high concentrate layers of Al to get exposed by hot damp conditions in the oxidation process enabled by the drilled holes (e.g., this Embodiment 3), or by the implant to render all other areas nonconductive (e.g., see Embodiments 1 and 2).

701Electrical Waveguide Substrate702Etched region isolating large single mesa from Ground Frame703N Metal contact electrically contacting N contact layer704N Mirror705N Contact layer in N mirror (low resistance for ohmic contact)706N Mirror above N contact region707Active region (quantum wells)708Oxidized Layer Closing off Current in these Regions709P mirror710Dielectric Layer711Plating on top of P contact Metal712Aperture in P Contact Metal and Plating Metal for laser beam exit713Electrical Waveguide Substrate714Ground Contact of GSG Electrical Waveguide715Signal Contact of GSG Electrical Waveguide716Solder-Bonding GSG Waveguide to Laser Chip717Solder-Bonding GSG Waveguide to Laser Chip718Frame structure electrically connected to N contact regionof laser chip

FIG.7A2is a continuation ofFIG. 7Aabove, and it further shows:

721Ground Contact of GSG Electrical Waveguide722Plating on Ground Contact of GSG Electrical Waveguide723Solder-Bonding GSG Waveguide to Laser Chip724Signal Contact of GSG Electrical Waveguide725Solder-Bonding GSG Waveguide to Laser Chip726Plating on Signal Contact of GSG Electrical Waveguide727Etched Hole Regions in Single Mesa Substrate permits oxidation toform Current Confinement Apertures728Plating on top of P contact Metal729Opening in Dielectric layer for electrical contact from Plating to PContact Layer on Laser Single Mesa Structure730Dielectric Layer731Oxidation Layer closing off current near Etched Hole Regions

FIG. 7Bis aFIG. 7cutaway view that also shows the electrical connections and electrical waveguide that are not shown inFIG. 7.FIG. 7Billustrates the cross section through the apertures created by the oxidized layer. The oxidized layer is exposed to the oxidation process through the holes in the single structure illustrated inFIG. 7A. This view also shows that the Active Mesa Structure is truly a Single Mesa Structure.FIG. 7Bdepicts:

751Ground Contact of GSG Electrical Waveguide752Plating on Ground Contact of GSG Electrical Waveguide753Solder-Bonding Ground of GSG Waveguide to Laser Chip754Signal Contact of GSG Electrical Waveguide755Plating on Signal Contact of GSG Electrical Waveguide756P contact Metal on Laser Chip757Opening in plating and P Contact Metal over Laser Aperture758Plating on P Contact Metal759Solder-Bonding Signal of GSG Waveguide to Laser Chip760Dielectric Layer Protecting Active Mesa Structure from N Contact761Current Confinement Aperture formed by opening in OxidationLayer762Oxidation Layer Dielectric763Laser Beam Propagating through Metal Opening

FIG. 7Cis a cross sectional view of the area where the P Contact or Signal of the GSG waveguide is positioned below the Laser Chip where the N Contact Frame or single structure mesa grounded to the N contact of the laser is above the GSG Electrical Waveguide. The large gap between the Laser Ground and the P Signal Pad reduces the capacitance of the circuit enabling higher frequency operation.FIG. 7Cdepicts:

780Dielectric Layer781N Type Ohmic Contact Metal782Plating Shorting N Metal Contact to Single Ground Mesa Structure784N Contact Layer in Epitaxial Growth785Plating Electrically Contacted to Signal Pad on ElectricalWaveguide786Metal Signal Pad Lead on GSG Electrical Waveguide787Plating on Ground Pad of GSG Electrical Waveguide788Electrical Waveguide Substrate789Gap between Conductive Signal Pad Structure and N ContactLayer Reduces Capacitance

Process for Embodiment 3 of US Pat App Pub 2017/0033535

An example embodiment of the process steps to create the single structure for embodiment 3 with oxidation current confinement can be as follows.Step 1. Use photolithography to mask areas which will not have P Metal deposited.Step 2. Deposit P Metal (typically TiPtAu ˜2000 A)Step 3. Photolithography lifts off and wafer cleaning. O2 descum or ash all organics off wafer.Step 4. Dielectric deposit (typically SiNx ˜<1000 A) used as an etch maskStep 5. Use photolithography to mask areas of dielectric which will not be etched.Step 6. Use plasma etch to etch through dielectric (typically Fl based etchant) can use wet etch such as BOE (buffered oxide etch).Step 7. Etch pattern into Laser or Light Emitting Diode Epitaxial material. Stop on Substrate or doped electrical contact layer. Typically the etch is Cl based with some (high percentage) amount of BCl3.Step 8. Clean off mask. O2 descum or ash all organics off wafer.Step 9. Use photolithography to mask areas which will not have N Metal deposited.Step 10. Deposit N Metal (Typically GeAu/Ni/Au eutectic composition of 80% Au/20% Ge by atomic weight. Total thickness of AuGe layer ˜3000 A or more with ˜200 A Ni or more of other diffusion barrier metal and ˜5000 A of Au or moreStep 11. Clean off mask (typically called lift off). O2 descum or ash all organics off wafer.Step 12. Dielectric deposit (typically SiNx ˜2000 A) used as a non-conductive isolation barrierStep 13. Use photolithography to mask areas of dielectric which will not be etched.Step 14. Use plasma etch to etch through dielectric (typically Fl based etchant) can use wet etch such as BOE (buffered oxide etch).Step 15. Clean off mask. O2 descum or ash all organics off wafer.Step 16. Use photolithography to mask areas which will not have Plated Metal deposited.Step 17. Plate areas with ˜4-5 um of Metal (typically Au) or Cu if diffusion barrier can be deposited first.Step 18. Use photolithography to mask areas which will not have Solder deposited.Step 19. Deposit Solder Metal (Typically AuSn/Au eutectic composition of 80% Au/20% Sn by atomic weight. Total thickness of AuSn layer ˜40,000 A (4 microns) or more with ˜500 A Au on top to stop any oxidation of Sn. This layer can be patterned and deposited on the submount with electrical waveguide which is bonded to the laser grid.Step 20. Separate laser chips from wafer with cleaving or dicing.Step 21. Design and Fabricate electrical waveguide to align to laser chip with the design to allow high frequency operation.Step 22. Align and Flip Chip Bond the laser chip to the Submount electrical waveguide

Embodiment 4 for US Pat App Pub 2017/0033535—Bottom-Emitting Oxidation

In a fourth embodiment, an oxidated single structure with multiple lasing regions is designed as a bottom-emitter rather than a top emitter.FIG. 8throughFIG. 14Cprovide details about Embodiment 4 and illustrate the process which can be used to make this embodiment. The lasing grid's light is emitted through the substrate forming a back emitter.

Light is transmissive in GaAs from wavelengths around 900 nm and greater. If the wavelength of the light engineered in the epitaxial design is in the range ˜900 nm and above, the GaAs substrate transmits the light or is transparent to the light. If the epitaxial design includes an N mirror that is less reflective than the P mirror, a laser such as a VCSEL can emit the light from the N mirror through the substrate. The laser beams will propagate through the material, and the substrate can be a platform for optical components to collimate, spread, diverge, converge or direct the light. This enables integrated optical circuits with extremely high bright power to be formed. The single structure and the ground contact can then be integrated to a high speed electrical waveguide substrate enabling high frequency responses from the entire grid. A ground signal ground electrical waveguide is ideal for this high speed electrical waveguide. Another type of electrical waveguide that may be used is a microstrip waveguide (seeFIG. 15), where the signal pad is separated from the ground pad by a thin dielectric layer on a substrate.

FIG. 8is an illustration of a typical epitaxial design. Any high speed design can be used for VCSEL devices.FIG. 8shows:

81GaAs substrate82Possible position for low resistance contact layer83N Mirror layer after contact region84Low resistance N contact region85N Mirror layer after quantum wells86Quantum Well Region87Oxidation layers88P Mirror89Low resistance P Contact layer

FIG. 9is an illustration of the first process performed, which is P metal deposit. This is typically a Ti/Pt/Au Layer on top of the highly P doped Contact Layer forming an ohmic contact.

91P Metal forming Ohmic Contact after annealing process92Low Resistance P Contact Layer

FIG. 10is a top view of the etch of the epitaxial layer down to the N contact layer.FIG. 10shows:

1001Etched Area to N Contact Layer1002Single Mesa Ground Structure1003Single Mesa Active Structure1004Etch Hole to Allow Oxidation Process to form Apertures1005Area in between all holes where there will be no oxidationwhich forms conductive current confinement

FIG. 10Ais a cross section view A ofFIG. 10formed before oxidation process, and FIG.10A2is a cross section view A ofFIG. 10formed after oxidation process. FIG.10A2shows:

120Oxidation completely closes off conductive path near anyetched regions that were exposed during the oxidation process.

FIG. 10Bis a cross sectional view B ofFIG. 10illustrating where the current confinement apertures were formed in the areas shown. This view represents a section of the single mesa where no holes are penetrating the cross section, and clearly shows that the mesa structure is a Single Mesa Structure enabling a more robust structure preferred at the bonding process.FIG. 10Bshows:

125Current Confinement Aperture is conductive region of SingleMesa Structure126Oxidized Layer forming as dielectric layer near where holeswhere etched127P Metal Contact Layer

FIG. 11illustrates the dielectric layer deposited and patterned with opened via “holes” for electrical contact to the epitaxial contact layers and sealing the semiconductor for reliability purposes.FIG. 11shows:

1101Dielectric Layer patterned with openings or “vias”1102Opening in Dielectric Layer to P Contact Metal1103Contact Layer on Single Mesa Ground Structure

FIG. 12shows the N metal contact after it has been deposited.FIG. 12depicts:

1201N Contact Metal is deposited over the N Contact via hole tomake an electrical connection to the N Contact Layer.

FIG. 13illustrates the next step of plating metal which shorts the N contact region to the top of the single grounded frame region, which will be bonded and electrically conductive to the ground pad of the GSG waveguide. The plating also adds height to the active region reducing capacitance and it removes heat from the active region of the devices to give the devices better performance. The plating over the active single structure is isolated from the N mirror and N contact region by the dielectric layer.FIG. 13shows:

1301Dielectric Layer preventing the Plating covering the ActiveRegion and extending into the holes of the single mesa structure1302Plating Covering Single Grounded Mesa Structure Shorted to NContact Region through N Contact Metal1303Plating Covering Active Structure and extending into the holesof the active region where cooling can occur through a higherthermal conductance of the plating metal1304Plated Metal extending over single frame structure for bondingand electrically connecting to ground of GSG electrical waveguide.

FIG. 14aillustrates solder deposited on the laser chip. This serves as the electrical conductive bonding adhesion layer between the laser chip and the high speed electrical waveguide.FIG. 14ashows:1401Solder deposit

FIG. 14billustrates the alignment of the GSG electrical waveguide before bonding.FIG. 14bshows:

1403Submount for GSG Electrical High Speed Waveguide1404Ground Pad for GSG Electrical High Speed Waveguide1405Signal Pad for GSG Electrical High Speed Waveguide1406Plating Metal Deposited on Conductive areas of GSGElectrical High Speed Waveguide

FIG. 14Cillustrates the bonded laser chip to the GSG electrical waveguide. The gap in the single grounded mesa enables high speed operation by reducing capacitance.

Embodiment 5 for US Pat App Pub 2017/0033535

In a fifth embodiment, a microstrip or strip line electrical waveguide is used rather than the GSG waveguide, as shown byFIG. 15. This embodiment can also have the gap mentioned inFIG. 14cabove. This electrical waveguide can also be formed by a ground layer below a thin dielectric with a signal lead on the top of the dielectric forming a strip line or microstrip waveguide. Openings in the dielectric can be used to contact the ground portion of the lasing grid. The width of the lines and thickness of the dielectric can be controlled to produce a specific impedance value for circuit matching characteristics. It should be understood that this technique can also be used for other embodiments, such as Embodiment 2 or any of the embodiments discussed below. The view inFIG. 15shows a cross section across the active single mesa structure:

151Waveguide substrate152Metal Ground Pad across the entire waveguide153Dielectric layer separating the Ground from the signal pads154Metal Signal Pad155Metal Plating on Signal pad156Solder electrically connecting the signal pad to the singleactive mesa shown here with gaps or holes etched into it.157Metal Plating on the Ground Pad158Solder electrically connecting the ground pad to the singlegrounded mesa

Embodiment 6 for US Pat App Pub 2017/0033535

FIG. 16shows a sixth embodiment. InFIG. 16the structure is unique in that it leaves paths for a portion of the light of each lase point to be directed to another laser next to it in order to keep the lasing in phase. In this example the laser161has some of its outer mode structure reflected162down to the laser aperture next to it163which produces light in phase with162. The laser which is in phase is164and in turn reflects from an angled reflective surface165back to the aperture of the laser next to it167which is also in phase with164and161and so on. An angular and or reflective area164just outside of the lens or output area can divert a small portion of the light which is overflowing from the lens or output diameter to the lasing grid adjacent to it, enabling a coherent lasing grid. Some of the light from the neighboring lasing points is injected into the lasing point which sets up the lasing points in a phase relation with each other. This allows a coherent operation of all lasing points when the structure directs some of the light from each laser to its neighbor. The reflectance, distance and angles are very precisely calculated by one skilled in the art of optical modeling. Coherent operation is a benefit which has eluded laser array operation for many years.FIG. 16shows:

161Large aperture laser with wide divergence only emitting a portionof the light162A portion of the light from laser 161 is reflected to aperture 163163Aperture of laser where reflectance conforms to the phase of thelight from 162164Large aperture laser with wide divergence only emitting a portionof the light165Angled reflective surface on the back of the laser chip just outsidethe output aperture166the reflected beam in phase with laser grid 164167Large aperture laser with wide divergence only emitting a portionof the light

Embodiment 7 for US Pat App Pub 2017/0033535

FIG. 17shows a seventh embodiment. InFIG. 17, the back side of the lasing grid chip has etched patterns to redirect the laser light172to particularly beneficial areas. This is accomplished by diffractive optical elements (DOE)171, which have the surface etched in a way that when light travels through that portion, the angle of the surface and redirects175beams or light depending on the angle of the surface of the DOE. This can be used to collimate or diverge, direct or homogenize the light.FIG. 17does not illustrate the electrical waveguide. The mode can be controlled by the aperture sizes and characteristics of the reflective surface173and174.FIG. 17shows:

171Redirected Laser Grid Beam from beam 172172Laser Grid Beam emitted from apertures173Contact and back of mirror for back emitting laser grid174Contact and back of mirror for back emitting laser grid175Redirected beams from laser grid

Embodiment 8 for US Pat App Pub 2017/0033535

FIG. 18shows an eighth embodiment. InFIG. 18, a patterned diffractive grating184(this is the opposite angular pattern thanFIG. 17's DOE) is placed or etched over the emission points181on the backside of the laser wafer in a back emitting VCSEL design which directs the lasing points outward185from the grid. From the lens it looks like all the lasers are coming from a single point186behind the chip to form a virtual point source where a macro lens187can be used to collimate the beam from the virtual converged source behind the chip.FIG. 18shows:

181Contact and back of mirror for back emitting laser grid182Aperture creating laser characteristics183Laser Beam from laser grid184Surface of Diffractive Optical Element (DOE) angled forspecific total beam grid characteristics185Redirected beams from laser grid186Converged virtual light source from all beams as seenfrom lens 187187macro lens with focal point on virtual convergencepoint 186

Embodiment 9 for US Pat App Pub 2017/0033535

FIG. 19shows a ninth embodiment.FIG. 19illustrates a cross section of the bonded etched and oxidized Embodiment 3, except it has microlens which have been processed on the back of the laser chip and positioned so that one is aligned to the other and one is slightly misaligned on purpose in order to redirect the laser beam emitted from the single mesa structure. While embodiment 3 is referenced for this arrangement, it should be understood that any of the above back emitting embodiments and a microlens array attached to the chip or positioned above the output grid can be used. The microlens array can have values related to the pitch of the light conducting grid points but with a slightly different pitch lens74forcing the light emitted by the lasing points to be directed to a single area where the beams come together or seem like they come together in front of the chip or behind the chip as in a virtual point source. If the microlens pitch is smaller than the laser pitch, it will guide the outlying lasers to a point in front of the chip or directed inward. If the microlens arrays pitch is larger than the lasers' grids' pitch, the light will be directed outward as inFIG. 19.FIG. 19shows:

71Laser Substrate72N Mirror73N Contact Region74MicroLens slightly offset from laser directing laser light outward75Active region or quantum wells76Oxidized layers creating current confinement into the active area77Etched trench creating isolation from the single ground structureand the active single mesa structure78P Metal Contact79Hole Etched into the single mesa structure to allow oxidation to occur80solder electrically connecting the laser chip and the High speedelectrical waveguide81Signal pad of the GSG electrical waveguide82P mirror83GSG Waveguide substrate84Plating shorting the N metal located on the N contact layer and thesingle ground mesa which is in electrical contact to the Ground Padof the GSG electrical waveguide85Ground Pad of the GSG electrical waveguide

Embodiment 10 for US Pat App Pub 2017/0033535

FIG. 20shows a tenth embodiment.FIG. 20illustrates that an extended cavity laser design can be implemented using the single grid structure by reducing the reflectivity of the N epitaxial output mirror230to a point where it will not lase, then adding the reflectivity to a reflective surface231on the back of the lasing grid which extends the cavity. This structure reduces feedback of the higher mode structure233in the cavity, thereby forming a more fundamental mode structure for the output beam235from the grid.FIG. 20shows:

230Arrow pointing to incomplete N output mirror epitaxial region.231Reflective region made of dielectrically layers with varyingindexes of refraction.232Cavity of laser beam now includes laser wafer materialextending the cavity for modal rejection.233Reflected higher order modes which are not reflected backinto the cavity234Single or lower order modes in the cavity235single or lower order modes outputted from the ExtendedCavity Device

Embodiment 11 for US Pat App Pub 2017/0033535

FIG. 21shows an eleventh embodiment. InFIG. 21, a VCSEL structure can be adapted to the laser grid design like the above embodiment, and the back of the lasing chip where the output reflector (deposited on top of lens shape241) of the lasing grid emits light can have convex241or concave features under the reflector to form better a focused (focus arrows243) feedback mechanism which rejects high modes and can be designed to have a single mode lasing output245from each grid area. The overall lasing structure will then have low M2 values. A lens or microlens can be added to collimate the output.FIG. 21shows:

240Arrow pointing to incomplete N output mirror epitaxial region.241Reflective region made of dielectrically layers with varying indexesof refraction deposited on top of microlens structure etched intothe laser substrate or wafer242Single mode beam being reflected within the extended cavity243light from edges being directed back into the single mode cavityfrom the optical element on the surface of the chip244single mode beam has more power and is more selective of thesingle mode than FIG. 20's single mode beam245Output of high quality single mode beams246highly reflective epitaxial mirror

Embodiment 12 for US Pat App Pub 2017/0033535

FIG. 22shows a twelfth embodiment. InFIG. 22, a VCSEL structure can be adapted to the laser grid design like the above embodiment except that the beams which exit straight out of the lens go through an external microlens array which has been designed with different pitch microlens than the laser pitches to allow redirection of the beams either to or from a single location like many of the above embodiments. Other forms of this technique could use a concave lens formed on the bottom of the external lens array which are aligned and have the same pitch as the laser grid, while a convex laser array with a different pitch than the laser grid is at the top. Another technique to direct beams would be to use DOEs as the top optical element instead of the convex microlens which are on the top of the external lens array.252is light reflected back into the center of the aperture making a stronger single mode beam while253has the reflective coatings which complete the laser output mirror cavity.254is the cavity and would have an antireflective coating deposited on the inside of the external lens cavity while also depositing an anti-reflective coating on the top microlens array. Another technique would be to use the flat reflective properties such as inFIG. 20to complete the cavity mirror and have the microlens array offset on the top or a DOE on top to redirect the beams.FIG. 22shows:

250Arrow pointing to incomplete N output mirror epitaxial region.251Single mode beam being reflected within the extended cavity252light from edges being directed back into the center creatingstrong single mode cavity from the optical element on the surface of thechip253Reflective region made of dielectrically layers with varyingindexes of refraction deposited on top of microlens structure etched intothe laser substrate or wafer254Cavity for etched lens to not touch external lens array255External lens array transmissive material256Single Mode beam outputted by extended cavity laser257Microlens from lens array with different pitch than laser pitchdirecting beams258Directed single mode beam