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Superconducting Thermal Spreader Enabled MWIR Band-IVb Quantum Cascade Laser with 65 W Average Output Power


OUSD (R&E) CRITICAL TECHNOLOGY AREA(S): Quantum Science; Directed Energy 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 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: Develop a high-performance, superconducting heat spreader to reduce the junction temperature of a BandIVb, almost beam diffraction-limited high-power quantum cascade laser that outputs average output power > 65 W with wall-plug efficiency (WPE) > 35% during high-repetition rate, pulsed-mode operation. DESCRIPTION: High performance Midwave Infrared Quantum Cascade Lasers (MWIR QCLs) relevant for various naval applications, such as directed infrared countermeasures (DIRCM), stand-off detection, or atmospheric optical communications, rely on QCLs' ability not only to generate light in midwave infrared atmospheric transmission windows, but to deliver a high degree of intensity focused to a small angular profile at a distance [Refs 1–3]. This requirement emphasizes a high brightness beam over pure power scaling. High continuous wave (CW) output power in QCLs is generally achieved with increases in wall-plug efficiency (WPE) utilizing a narrow-ridge waveguide. Such approaches have led to CW powers of ~5 W [Ref 4]. Also, power scaling of a single QCL device has been demonstrated as a new promising route to further increase in power through the geometry of the QCL core by reducing the number of superlattice periods while simultaneously expanding the breadth of the device [Refs 5–7]. These so-called broad-area devices manage the inherent thermal constraints of CW operation by manipulating the heat flow out of the laser core with the changing geometry. Manipulation of the laser core geometry has been shown to ensure brightness for these devices by adjusting mode competition in favor of the fundamental transverse mode in a way compatible with CW power scaling. > 7 W of CW optical power in a high-quality beam have been demonstrated from a single broad-area QCL emitter, and model projections show that up to 15 W can be achieved from a fully optimized device. For many defense applications, a signal modulated at MHz frequencies with high-duty cycle (over 40% or higher) is a compatible replacement for CW operation due to the laser modulation frequency exceeding the required sampling frequency of the sensor/detector. The operating space between a negligibly small duty cycle and CW, shows promise as an excellent avenue for the significant enhancement of average power by regulating the transient temperature of the laser with a large duty cycle, quasi-CW (QCW) operation. This can optimize the tradeoff between laser pulse uptime and a cooling cycle to reduce temperature buildup that degrades laser performance. In addition, average power may be increased by a substantial amount, while simultaneously reducing the need for input power by driving the device in a pulsed mode with high-repetition rate. The cooling cycle that occurs when the laser is not being driven, reduces the temperature of the laser, enhancing peak power to a degree where average power achieved is higher than that of CW conditions. The enhancement to WPE is significant in this pulsed operation because the increased average power is achieved by reducing the average energy input from CW conditions. However, the legacy MWIR QCL devices optimized for CW operation will not show much significant improvement in average power when operated in quasi-continuous wave (QCW) mode as average power for such devices peak at 100% duty cycle, that is, in CW mode of operation. Therefore, the entire laser structure, including the active region stage and waveguide designs, have to be optimized for QCW operation. In addition to the advances in the QCL physics and designs, many recent advances in thermal management can be leveraged, such as vapor chambers, Ag-diamond alloys for CTE-matched submounts, novel phase change materials for efficient active heat extraction, and so forth [Refs 8 & 9], to push the aggregate performance envelope of QCLs. It is the also the goal of this SBIR topic to develop active cooling superconducting heat spreaders, of which the thermal conductivity should exceed the commonly used AlN, Cu, or CuW substrates (140-180 W cm-1 K-1) by at least a factor of 10. The final packaging solutions should enable efficient extraction of at least 200 W of dissipated power. The proposed laser and heat spreader solutions need to assure reliable operation in a variety of environmental conditions, which includes operation under high g-forces [Ref 6]. Combining a superconducting heat spreader with a high-performance QCL operating at QCW mode, can elevate the device performance with average output power and WPE to an unprecedented level. Finally, this paradigm-shifting approach of agglomerating active superconducting heat spreader with a high-performance QCL in QCW mode, will enable the elimination of the use of an active water cooling system, resulting in up to a factor of five in size and weight of the overall laser cooling system configuration. PHASE I: Demonstrate feasibility of modelling and simulation on thermal management and packaging solutions that would allow for efficient extraction of at least 200 W of dissipated power. Design the thermal management packaging solution that should include active cooling heat spreader with—at a minimum—over 10X improvement over conventional submount heat spreader. The solutions should include an overall QCL cooling subsystem that does not include any active water cooling, and has lower size and weight compared to the current conventional cooling solution. The active cooling solution design should enable the demonstration and delivery of QCL with WPE of 35% operating at QCW mode with the required duty cycle and with 65 W average output power at 30 C for at least ten minutes. Technological risks, reliability concerns of the proposed solution, and future transfer to manufacturing process should be discussed in depth. Also, demonstrate a 4.6 µm QCW QCLs delivering over 10 W of average power. The Phase I effort will include prototype plans to be developed under Phase II. PHASE II: Optimize the QCL and superconducting substrate design. Fabricate, demonstrate, and deliver a packaged prototype of a 4.6 µ QCL system delivering over 65 W of average power operating in QCW mode with the required duty cycle and with beam quality of M2 < 1.5 for an aggregate ON cycle exceeding ten minutes. PHASE III DUAL USE APPLICATIONS: Transition the technology for DoD use. Assist in applying the design for specific system applications such as countermeasures. This is expected to entail selection of device performance parameters, and adjustment of corresponding process parameters, in order to produce the required quasi-continuous output power at the optimum Phase IVb wavelength. The final product will be a high-performance laser device of which the output power can be scaled, if necessary, via beam combining for current and future generation DIRCMs, LIDARs, and chemicals/explosives sensing. The commercial sector can also benefit from this crucial, game-changing technology development in the areas of detection of toxic gas environmental monitoring, non-invasive health monitoring and sensing, and laser spectroscopy. REFERENCES: 1. Ostendorf, R.; Butschek, L.; Hugger, S.; Fuchs, F.; Yang, Q.; Jarvis, J.; Schilling, C.; Rattunde, M.; Merten, A.; Grahmann, J.; Boskovic, D.; Tybussek, T.; Rieblinger, K. and Wagner, J. “Recent advances and applications of external cavity-QCLs towards hyperspectral imaging for standoff detection and real-time spectroscopic sensing of chemicals.” Photonics, Vol. 3, No. 2, June 2016, p. 28. 2. Martini, R., & Whittaker, E. A. (2005). Quantum cascade laser-based free space optical communications. In Free-Space Laser Communications (pp. 393-406). Springer, New York, NY. 3. Grasso, R. J. (2010, October). Source technology as the foundation for modern infra-red counter measures (IRCM). In Technologies for Optical Countermeasures VII (Vol. 7836, p. 783604). International Society for Optics and Photonics. 4. Bai, Y., Bandyopadhyay, N., Tsao, S., Slivken, S., & Razeghi, M. (2011). Room temperature quantum cascade lasers with 27% wall plug efficiency. Applied Physics Letters, 98(18), 181102. 5. Suttinger, M., Go, R., Azim, A., Sanchez, E., Shu, H., & Lyakh, A. (2019, May). High brightness operation in broad area quantum cascade lasers with reduced number of stages. In CLEO: Applications and Technology (pp. AW3P-2). Optical Society of America. 6. Suttinger, M. M., Go, R., Figueiredo, P., Todi, A., Shu, H., Leshin, J., & Lyakh, A. (2017). Power scaling and experimentally fitted model for broad area quantum cascade lasers in continuous wave operation. Optical Engineering, 57(1), 011011. 7. Masselink, W. T., & Semtsiv, M. P. (2018, October). Power and brightness scaling of quantum cascade lasers using reduced cascade number and broad-area emitters (Conference Presentation). In Technologies for Optical Countermeasures XV (Vol. 10797, p. 1079703). International Society for Optics and Photonics. 8. Han, L., Gao, G., Li, C., Zhang, Y., & Geng, H. (2019, June). PCM cooling system of high-power lasers. In High-Power, High-Energy, and High-Intensity Laser Technology IV (Vol. 11033, p. 110330V). International Society for Optics and Photonics. 9. Oshman, C., Li, Q., Liew, L. A., Yang, R., Lee, Y. C., Bright, V. M., Sharar, D. J., Jankowski, N. R., & Morgan, B. C. (2012). Thermal performance of a flat polymer heat pipe heat spreader under high acceleration. Journal of Micromechanics and Microengineering, 22(4), 045018. KEYWORDS: Superconducting Thermal Spreader; High-Brightness; High-Efficiency; Mid-Wave Infrared; Band-IVb; Quantum Cascade Laser; Quasi-Continuous Wave Operation
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