FA8650-19-S-1013-Atch7.pdf

Attachment 7 Statement of Objectives

A-GMLRD

Asynchronous Geiger Mode LADAR Receiver Development (A-GMLRD) Statement of Objectives (SOO)

31 January 2019

1. Introduction:

The Asynchronous Geiger Mode LADAR Receiver Development (A-GMLRD) project will develop a packaged light detection and ranging (LiDAR) receiver system(s) for laser detection and ranging (LADAR) and laser communications (lasercom) applications. The intent is to conduct a technology transfer of Geiger mode receiver technology from MIT Lincoln Laboratory (MITLL) to industry, developing Geiger mode receivers for military use. The result will yield a photon sensitive receiver capable of providing high precision timing measurements to objects within the sensor field of view (FOV), supporting Air Force sensor development programs. ITAR does apply to aspects of the design and hardware.

2. Background:

The Department of Defense has sponsored research of active electro-optic sensors for many applications, including ranging to surfaces, target identification, mapping, and communications. Development of single photon sensitive avalanche photodiodes (APDs) has been explored for multiple decades, and application of APDs for LiDAR has been significantly researched by MITLL through their development of Geiger mode avalanche photodiodes (GMAPD) for use as LiDAR and lasercom receivers. GMAPD arrays are capable of detecting extremely low flux returns from surfaces illuminated with transmitted laser signals, which extends to the capability of detecting single photon events for each detector while operating at large detection bandwidths. In the LiDAR applications, these low flux returns are time correlated to a transmitted laser pulse reflecting from a target or surface area. Similarly, for the lasercom applications, GMAPDs provide the opportunity to time stamp photon arrivals between a transmitter and receiver along any portion of the laser path. Processing of the timing event data results in information which is then exploited for numerous mission types, including LiDAR and communications applications. Processing the data can also provide intensity images for analysis and integration with other sensing modalities.

The primary implementation of GMAPD receivers has been toward framed imagers. With framed operation, all detectors within the detector array are armed at some point in time after the transmitted laser signal has been created, providing an ability to detect objects within a specified range gate located some distance from the sensor. The ability to shorten a range gate lessens data generated by the sensor while also aiding the ability to reduce effects of noise. Through improvements in detector and ROIC design, research has expanded into development of asynchronous mode GMAPD receivers. The asynchronous modality allows each GMAPD to individually rearm itself after a predetermined reset time following a photon detection. Although asynchronous mode operation produces extremely large volumes of data, this receiver design is capable of supporting additional sensing applications. Development of processing algorithms has correspondingly improved, sufficient for utilization of asynchronous Geiger mode LiDAR and lasercom receivers in research and development efforts through technology readiness level (TRL) 6.

3. Scope:

This project seeks to develop photon counting GMAPD receivers for military sensing applications. The receivers are to function as Geiger mode LiDAR receivers and/or lasercom receivers, ultimately providing sensing capabilities from land-based, aerial, and space platforms. This effort includes development of GMAPD receivers, receiver component model development, electrical and optical characterization of sensor performance, and testing of packaged laboratory class receiver.

The receivers will support sensing modalities to address gaps identified in Globally Integrated Intelligence Surveillance and Reconnaissance, Global Precision Attack, Special Operations, Air Superiority, and Space Superiority service core functions. The sensing modalities include direct detection LADAR, synthetic aperture LADAR, vibrometry, laser communications, and other applications involving 1-D, 2-D, or 3-D LADAR. The sensing modalities directly support the mission applications of combat identification, foliage penetration, aerosol detection, wind sensing, localized mapping, communications, and battle damage assessment. The generated sensor data must be capable of being processed and interpreted in order to support those mission applications. The LiDAR sensor will output data which can be processed for use with point cloud viewers, automated target recognition (ATR) and aided target recognition (AiTR) algorithms, potentially for near real-time processes, and other algorithms supporting the respective mission application. The lasercom sensor will output data which can be processed for use in communications, supporting communications protocols such as pulse position modulation. The sensor systems will support missions of low, medium, and high altitude aerial platforms with potential commercialization to space platforms and ground platforms.

4. Objectives:

Develop GMAPD receivers for military use, supporting sensor requirements for service core functions and AF research efforts.

The Government has a need for receivers operating in an asynchronous Geiger mode with applications in imaging, laser communications, and other sensing applications requiring high sensitivity and high data rates. The LiDAR direct detection and imaging capability requires a sensor which can output data capable of being processed for use with existing coincidence processing algorithms in order to produce point clouds and other data products which are viewable through existing application software such as QT Modeler® and similar viewers. Coherent LADAR requires sufficient pixel bandwidth to process data for applications including wind sensing, synthetic aperture LADAR, and vibrometry. Lasercom also requires sufficient per-pixel bandwidth to process the data for time-of-arrival based communications.

It is a goal of this research effort to productize asynchronous Geiger mode receivers, provide path toward packaging and hardening a receiver system for use and operation in military systems, develop commercialization plans, and project conceptual improvements for manufacturing of a packaged receiver for relevant environments. The objective sensor system supporting lasercom projects should target volume production when developing a commercialization plan.

Incorporation of the Geiger mode receivers into near-term research projects as well as future projects require sufficient physics based analysis, performance based analysis, and documentation of the Geiger mode receiver to support those development efforts. Future trades may include insertion into larger sensor systems, development of new sensor systems, determine performance expectations of those sensor systems, and development of the evaluation processes of those sensor systems.

5. Requirements and Constraints:

The A-GMLRD project may award up to 2 contracts, each with a 24 month technical period of performance (PoP) plus a 3 month reporting period. AFRL is seeking sources for an asynchronous Geiger mode receiver which meets or exceeds the characteristics detailed within this SOO and in Appendix A. It is expected that complex designs may require iterative development, where results from analysis of test articles may provide insight into improvements in the overall receiver design. Representative properties of a receiver system are shown in Appendix A, Table 1.

Technical proposals should include expected performance and derivation thereof. Performance expectations should include threshold and objective values, and discussion of design implementation. The receiver is to be capable of operation within systems which implement other sensor modalities and ancillary data. It is desired that the final packaged receiver systems are at least TRL 4 and capable of operation in a flight environment and outdoor environment, where such operation will be performed external to this contracted effort. No airworthiness requirement exists under this contract.

Proposals should include a development schedule, development cost, TRL rating, risk identification, and risk mitigation strategies.

6. Period of Performance (PoP):

The overall development effort will span a 27 month PoP (24 month technical PoP + 3 month final report).

7. Deliverables:

CDRLs, hardware, and software.

Hardware: At least 2 packaged receiver systems from each contract.

Software: firmware, interface software, and application software.

Contractor deliverables are given in Table 1. Monthly, Bi-Monthly and Quarterly status reports shall be delivered not later than the 10th day of the first month of the next period. CDRLs listed in BAA FA8650-19- S-1013 that are not relevant to this SOO have been omitted.

Table 1. Deliverables

Item # Item Description Delivery or Support

A001 Final Report At Contract End

A002 Funds And Man-Hour Expenditure Report Monthly

A003 Status Report Bi-Monthly

A004 Data End of Tech Period

A005 Presentation Material As Required

A006 LC IRST Testbed Hardware End of Tech Period

A007 Scientific and Technical Reports (Receiver System User Manual)

End of Tech Period

A010 Source Code And Executable Software End of Tech Period

A013 Software User Manual (SUM) End of Tech Period

A014 Software Design Description (SDD) As Required

CLIN

Hardware (Software Development Environment) End of Tech Period

8. OPSEC Statement for AFRL/RY Contracts:

General Operations Security (OPSEC) procedures, policies and awareness are required in an effort to reduce program vulnerability from successful adversary collection and exploitation of critical information.

OPSEC will be applied throughout the life cycle of the contract. The Critical Information List (CIL) will be provided upon request by AFRL/ RYOY Information Protection Office. While working on the government installation, OPSEC guidance will be provided by AFRL/RYOY Information Protection Office.

9. SAFETY:

System Safety/Environmental Requirements. The contractor must comply with all federal, state and local safety and environmental regulations. The contractor shall prepare and submit an approved Safety Plan IAW AFI 91-202 AFRL Supplement 1 before any experiment may be conducted. The contractor shall comply with all Air Force safety and environmental regulations. The contractor shall comply with system safety requirements contained in MIL-STD 882E, Section 4 “General Requirements” for any deliverable systems or hardware. The contractor shall identify safety-critical components of those systems or hardware, and software interfaces with those components. The contractor shall test and verify the safety-critical hardware and software for safety acceptance.

Appendix A: Performance Goals Project Title: Asynchronous Geiger Mode LADAR Receiver Development (A-GMLRD)

LiDAR Sensor Performance:

MIT Lincoln Laboratory (MITLL) has conducted extensive research in design and implementation of Geiger mode avalanche photodiode (GMAPD) light detection and ranging (LiDAR) receivers and systems.

Improvements to those designs could benefit manufacturability and efficiency toward productization of receivers yielding low cost sensors for lasercom and other military applications. Government furnished equipment (GFE) items and Government furnished information (GFI) will be available for the A-GMLRD development effort. GFE includes 1 set of APD array and readout integrated circuit (ROIC) items. GFI in the form of a technical data package (TDP) of an existing MITLL asynchronous Geiger mode receiver are available, however improvements to those designs toward mission applications and manufacturability are necessary. The TDP also includes knowledge of supporting electronics requirements, data interfaces, data requirements, and processing requirements of a full receiver package. Alternative designs to the existing asynchronous Geiger mode ROIC may be considered, however, the documented performance of those alternative designs should meet or exceed the performance and specifications listed in Table 1.

Performance aspects of LiDAR receivers are used to model LiDAR sensor systems, drive system requirements, and determine applicability toward sensing applications. The primary performance metrics of GmAPD detectors are the dark count rate (DCR, the rate at which an individual APD registers a count without illumination) and the photon detection efficiency (PDE, the fraction of incident photons detected by an APD). Understanding and mitigating receiver noise is imperative to success in design. In addition to DCR and PDE, crosstalk and afterpulsing (a correlated noise phenomenon in GMAPDs) are additional noise sources. Detector crosstalk exists due to optical effects and electrical effects. One measure of detector crosstalk is the probability that a crosstalk event occurs within an NxN pixel region centered on the initiating pixel. The size of the region and probability of crosstalk which limit the utility of receiver depend on the application but a nominal utility threshold is < 10% probability in a 9x9 pixel region. PDE and DCR should be reported at the same operating point and described in terms of the statistical distribution across the focal plane array (FPA), e.g. a histogram of pixel DCR and PDE values. Overbias and temperature are the key variables. While PDE can be measured at an individual pixel level, receiver PDE is referenced to the input the sensor package, incorporating all the losses due to microlens coupling and packaging as well as intrinsic Geiger mode APD performance. The method used to determine PDE should be sufficiently described to ensure crosstalk events or afterpulsing events are excluded from the estimate. The description should include specified temperature and overbias, and technique to remove crosstalk and afterpulsing effects. A representative design point for DCR and PDE are DCR = 10 kHz (median), and a PDE = 25% (median) where 80% of the pixels have > 15%. Measurements of DCR and PDE must be performed under the same operating point and temperature conditions. Additionally, an analysis of detector PDE prior to bonding of the microlens array aids in development of receiver models.

Table 1: Properties for Asynchronous Geiger Mode LiDAR Receiver Parameter Value Goal array format 32x32 pixel pitch 100 um wavelength 1550 nm DCR 10 kHz median

PDE (note 1) 25% median APD timing jitter < 350 psec rms

Fill factor 100% Crosstalk < 1% (note 2)

Note 1: Goal of 25% median, with 80% of the pixels > 15%. PDE measurement must correlate to DCR measurements.

Note 2: Probability of a crosstalk event in a 9x9 region around a primary pixel of less than 1%

Readout Integrated Circuit (ROIC):

The use of an existing ROIC reduces program cost and schedule while bounding the design space for the detector arrays. The current asynchronous ROICs available from Global Foundries are of a 32x32 format consisting of 100 um pixel pitch (square), as listed in Table 2. The ROIC design incorporates a single bond pad per pixel, and connections on 2 sides of the array for common anode configurations providing interconnect to the ROIC. Common cathode configuration may be supported with additional modification.

The ROIC does not incorporate fuses for the detector circuitry and are not a requirement for the GMAPD sensor package design, however, the incorporation of fuses could be addressed in future versions.

Table 2: ROIC Parameters

Parameter Value array format 32x32 pixel pitch 100 um arm voltage up to 6.6 V*

* Max usable arm voltage depends on breakdown voltage uniformity and the requirement not to dc bias any pixels into Geiger mode.

Sensor Chip Assembly (SCA) Development:

Fabrication experiments aid in the development of APD arrays and ROIC improvements through exploration of design aspects and refinement of fabrication processes. Hybridization of detector arrays to the ROIC has been demonstrated using thermo-compression bonding with indium bumps deposited on the APD array to pads plated-up on the ROIC. Other bonding methods may be explored.

Evaluation of the SCAs prior to integration into packaged receivers reduces manufacturing risk.

Improvements to the MITLL ROIC designs require scientific models of the ROIC circuit designs and an in-depth analysis of the circuit designs. Low-cost experimentation may be performed to determine benefits of

ROIC modifications through modeling and through fabrication experiments of test circuits. Exploration of updates to ROIC designs can aid in the determination of alternate detector designs and alternate SCA packaging methods. Electrical testing of the test circuits would provide benefit toward performance model verification.

Development of Sensor Performance Expectations:

Physics based models, performance models, and simulations aid in providing sufficient analysis to show expected performance, operation, and limitations of an APD array, SCA, and receiver toward implementation in a larger sensor system. The resulting information can be utilized to improve system level designs, and aid in the evaluation and testing of GMAPD receivers for asynchronous Geiger mode LiDAR operation and for laser communication operation.

Receiver Integration into a LiDAR Sensor System:

In order to facilitate integration with sensor systems, GMAPD receivers are require to provide high bandwidth communication for readout of data, software control, and diagnostic capability of the receiver.

Representative signals are listed in Table 3. A graphical user interface for the receiver aids in the operation of the receiver for independent testing and characterization of system performance. Software libraries also aid in the development of LiDAR systems under subsequent projects. Datasheets, user manuals, interface control documents (ICD) or similar documentation for each sensor model aid integration of the receiver into larger systems.

Table 3: Receiver Wired Connections signal interface notes input clock connector Facilitate operating modes output clock connector input trigger connector Facilitate t0 from laser output trigger connector data (frame data) connector I/O controls connector status LEDs physical e.g., power, over temp., comm.

I/O connector(s) connector Camera Link HS, 4GigE, USB 3, other

It is a benefit of a LiDAR receiver to have the capability of generating sensor data for use with existing coincidence processing algorithms, where further processing of that LiDAR data is viewable in Quick Terrain Modeler® and in similar point cloud viewer application software, supporting usage of LiDAR data with ATR and AiTR algorithms. A packaged receiver system capable of operating in a flight environment can be utilized to collect representative LiDAR data and significantly aids in the development of LiDAR system requirements. Testing, characterization, and evaluation of the receiver system aids in model verification and in determining fidelity of the models, and benefits subsequent projects which may use the receiver system in larger sensor systems. Characterization of the receiver is needed in order to determine aspects of sensor hardening. Recommendations of hardening for flight and for space environments will benefit subsequent projects.

Future Manufacturability:

Demonstrations of manufacturing processes for Geiger mode LiDAR and communications receivers (aerial and space) aid in determining key yield, throughput, and cost drivers. Identification of manufacturing process improvements needed to meet yield/cost targets will aid in determining a plan toward manufacturability. A Manufacturing Readiness Assessment at a production facility will also provide benefit toward planning manufacturability improvements. Future exploration of detector designs may benefit additional integration efforts, such as extending detector wavelength to the 2.0 um to 2.4 um waveband.