RT&L FOCUS AREA(S): Control and Communications, Microelectronics, Network Command TECHNOLOGY AREA(S): Electronics, Information Systems, Materials, Sensors The technology within this topic is restricted under the International Traffic in Arms Regulation (ITAR), 22 CFR Parts 120-130, which controls the export and import of defense-related material and services, including export of sensitive technical data, or the Export Administration Regulation (EAR), 15 CFR Parts 730-774, which controls dual use items. Offerors must disclose any proposed use of foreign nationals (FNs), their country(ies) of origin, the type of visa or work permit possessed, and the statement of work (SOW) tasks intended for accomplishment by the FN(s) in accordance with section 3.5 of the Announcement. Offerors are advised foreign nationals proposed to perform on this topic may be restricted due to the technical data under US Export Control Laws. OBJECTIVE: Effort seeks to examine and utilize photonic components available today for application in cryogenic environments of high performance infrared sensor arrays. DESCRIPTION: Data rate demands of high performance Army imaging sensors have historically increased exponentially and are expected to continue doing so. Infrared sensors are being tasked with performing multiple functions simultaneously and at ever increasing pixel counts. Higher frame rates allow for additional applications but come with the cost of increased power usage. Army sensors today currently rely on electrical outputs for data transmission of scene imagery information to downstream electronics. Electrical output lines can only output so much data per channel, and thus the number of output lines have increased dramatically creating additional power consumption. An alternative solution to an impending data management bottleneck is conversion of digital read-out integrated circuit (ROIC) output signals to an optical data stream harnessing commercially matured photonic components. An optical output link ensures that future high performance imaging data rate demands can be easily met and is scalable to match sensor application demands. Additionally, optical data outputs enable flexible system design, are not susceptible to EMI interference, and exhibit excellent energy efficiency. Optical signal processing has been adopted by datacom and telecom industries to provide enormous data rates with superior energy efficiency to electrical transmission. Modulation and transceiver components have matured significantly but the photonic components that are offered commercially today are typically designed for room temperature application and their performance at the cryogenic temperatures required for the highest performance infrared sensors is undocumented. Furthermore, foundry offerings vary in terms of the types of photonic modulators available, whether components are custom or incorporated into the foundry Process Design Kits (PDKs), their compatibility with mixed signal design elements, and their degree of integration. In order to overcome the engineering challenge of harnessing photonic components, there is a need to document the performance and integration level being offered today so that future programs can reduce the technical risk of converting to optical outputs. The barrier to making the switch from electronics to photonic interconnects has yet to be overcome. Programs of record for infrared focal plane array (IRFPA) sensors often elect to settle for smaller evolutionary improvements in cryogenic electronic communications, instead of the leap-ahead capabilities available with high-speed, low energy cryogenic photonic links. IRFPA sensor development programs need compelling evidence to fully motivate the transition to this new technology. This project aims to inform Army sensor programs of the most suitable approach for incorporating these optical components. By testing pathways today, we can determine the readiness level of the various foundry offerings moving forward. In addition to a comprehensive study of available offerings, this work will also demonstrate the most suitable optical output link in a laboratory setting using appropriate transmission protocols. This demonstration will be performed at cryogenic temperature and will have a satisfactorily low bit-error rate. PHASE I: In Phase I performers will evaluate potentially feasible schemes to implement optical modulation in a cryogenic environment. In addition to evaluation, performers will begin preliminary work in acquiring hardware and software required for conversion of digital data to optical output link. All solutions must be compatible with current and future read-out integrated circuit technology, including necessary interface transmission protocols, practical signal modulation driving, and compact floorplan of integration. Solution must be suitable for use alongside sensor read-outs used in relevant Army programs. With the goal of maximizing system integration, team will preliminarily assess and design elements based upon viable foundry offerings or epilayer vendor procurement. Evaluation and design in Phase I should not be limited to a single source but should cover the commercial landscape to include all reasonably feasible solutions that can provide error-free performance. Bit error-rates must be lower than 1E-10 with the goal of being equal to or lower than 1E-12. In all cases, energy per bit and total system energy costs should be minimized and data transmission solution scheme must be able to reach modulation efficiency of less than 600 fJ per bit. By the end of Phase I, performers are expected to have comprehensively presented solutions to meet program expectations, began component design, clearly presented on the level of integration and energy usage analysis, provided a detailed test characterization plan, and initiated dialogue with foundry and/or material vendor business departments for acquiring components in Phase II. PHASE II: In Phase II, performers will acquire necessary photonic components from commercial foundries and begin systematic performance testing of various modulation schemes at cryogenic temperatures. Test temperatures must be relevant to high performance infrared sensor arrays. Coupling, insertion, and chip-to-chip losses will be documented alongside component power consumption to better understand system energy budget. On-off keying and tunability at cryogenic temperatures will be fully reported. A comprehensive performance and energy report detailing component results from different foundries will also include realistic configuration analysis of integrating alongside existing ROIC technologies. Development and integration of photonic components should be as monolithic as possible. Following presentation of performance and integration report for all explored foundry and scheme solutions, a single optical modulation scheme will be selected for laboratory demonstration at cryogenic temperature to include bit error rate testing. Demonstration effort should replicate infrared camera system as much as possible. PHASE III DUAL USE APPLICATIONS: This project is expected to significantly mature the engineering and integration challenges of converting digital sensor data to optical data transmission outputs. The findings of this effort will inform future high performance sensor programs on best practices to lower technology risk and give Army sensor programs confidence to implement this revolutionary change to sensor data management moving forward. This project naturally pairs with the highest data demanding sensors with broad applications in surveillance, wide field-of-view sensors, fast-event detection, targeting, and tracking. Near term transition pathways include airborne sensor packages with targeting and tracking requirements, such as Apache and Future Vertical Lift, which would benefit from being operated at higher frame rates than are currently possible. Superior energy efficiency of optical data outputs will also lower dewar cooler assembly energy budget, thus increasing system lifecycle, and appeal to sensor programs with moderate data rates and volume units, such as PM GS and PM TS sensors. REFERENCES: Chakraborty, U., Carolan, J., Clark, G., Bunandar, D., Gilbert, G., Notaros, J., ... & Englund, D. R. (2020). Cryogenic operation of silicon photonic modulators based on the DC Kerr effect. Optica, 7(10), 1385-1390. Eltes, F., Villarreal-Garcia, G. E., Caimi, D., Siegwart, H., Gentile, A. A., Hart, A., ... & Abel, S. (2020). An integrated optical modulator operating at cryogenic temperatures. Nature Materials, 19(11), 1164-1168. Estrella, S. B., Dorch, T. P., Cooper, T. M., Renner, D. S., & Schow, C. L. (2021, June). Novel Link Architecture Minimizing Thermal Energy Dissipation for Cryogenic Optical Interconnects. In Optical Fiber Communication Conference (pp. F2E-3). Optical Society of America. Fard, E. M., Long, C. M., Lentine, A. L., & Norwood, R. A. (2020). Cryogenic C-band wavelength division multiplexing system using an AIM Photonics Foundry process design kit. Optics Express, 28(24), 35651-35662. Fu, W., Wu, H., Wua, D., Feng, M., & Deppe, D. (2021). Cryogenic Oxide-VCSEL for PAM-4 Optical Data Transmission over 50 Gb/s at 77 K. IEEE Photonics Technology Letters Fu, W., Wang, H. L., Wu, H., Srinivasa, A., Srinivasa, S., Feng, M., & Deppe, D. (2020, September). Cryogenic 50 GHz VCSEL for sub-100 fJ/bit Optical Link. In 2020 IEEE Photonics Conference (IPC) (pp. 1-2). IEEE. Gehl, M., Long, C., Trotter, D., Starbuck, A., Pomerene, A., Wright, J. B., ... & DeRose, C. (2017). Operation of high-speed silicon photonic micro-disk modulators at cryogenic temperatures. Optica, 4(3), 374-382. Georgas, M., Leu, J., Moss, B., Sun, C., & Stojanovi , V. (2011, September). Addressing link-level design tradeoffs for integrated photonic interconnects. In 2011 IEEE Custom Integrated Circuits Conference (CICC) (pp. 1-8). IEEE. Johnston, A. R., Liu, D. T. H., Forouhar, S., Lutes, G. F., Maserjian, J. L., & Fossum, E. R. (1993, October). Optical links for cryogenic focal plane array readout. In Infrared Detectors and Instrumentation (Vol. 1946, pp. 375-383). International Society for Optics and Photonics. Wright, J. B., Trotter, D. C., Zortman, W. A., Lentine, A. L., Shaner, E. A., Watts, M. R., ... & Peckerar, M. (2012, June). Cryogenic operation of silicon photonic modulators. In Integrated Photonics Research, Silicon and Nanophotonics (pp. IM2A-5). Optical Society of America. KEYWORDS: Sensors, Photonics, Optical Modulators, Digital Read-outs, Cryogenic, Data Transmission
