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High Power Quantum Cascade Lasers in the Spectral Range between 3.8 and 4.1 Microns



OBJECTIVE: Develop quantum cascade lasers in the in the 3.8-4.1 micron wavelength range with high output power and brightness. 

DESCRIPTION: High-power, cost-effective, compact, and reliable mid-wave infrared (MWIR) Quantum Cascade Laser (QCL) platforms operating in the continuous wave (CW) regime are highly desirable for current and future Navy applications. Individual QCLs emitting within the 4.6-5 micron wavelength band with about 5 Watts CW output power and a wall-plug efficiency of about 20% at room temperature (RT) have been demonstrated [Ref 1]. Another shorter MWIR spectral band between 3.8 and 4.1 microns is of interest for Naval applications. The atmospheric transmission in this band is about 45% to 50% higher than that of the 4.6-5 micron spectral band. Furthermore, when QCLs emitting in both of the MWIR bands are beam-combined, higher emission power of QCLs in the 3.8-4.1 micron wavelength band [Ref 2] could alleviate the emission power, and their size, weight, and power (SWaP) dissipation requirements of QCLs in the 4.6-5 micron wavelength band. Despite their importance, very little technology development and advancement have been made for QCLs emitting in the 3.8-4.1 micron MWIR band, in stark contrast to their counterparts in the 4.6-5 micron band. Therefore, the QCL performance in the 3.8-4.1 micron band significantly lags those in the 4.6–5 micron band. The highest reported continuous wave wall-plug efficiency is less than 7% [Ref 2] and typical CW optical power for commercial state-of-the-art 4-micron QCLs is less than 1 Watt (W) [Ref 2]. The performance and thermal characteristics of the QCLs in the shorter end of 4 micron spectral range are significantly poorer compared to those at the 4.6 micron range due to the following critical factors. 1. To accommodate the larger transition energies (shorter emission wavelengths), strong confinement of carriers in QCL active regions is necessary to curtail excessive carrier leakage through parasitic energy states located above the upper laser level. Strong carrier confinement requires deeper wells and taller barriers, which in turn creates highly strained epitaxial layers, which need optimized crystal growth conditions to prevent misfit dislocations within the laser core. 2. The high strain layers (with strain >1.5%) layers throughout the QCL core region [Ref 2] result in significantly lower thermal conductance [Ref 3] which, in turn, gives rise to wide electroluminescence spectra and subsequently high threshold-current densities, as the temperature of the active region rises [Ref 2]. 3. Factors (1) and (2), combined with inherently higher drive voltages, have led to the CW power and wall-plug efficiency values of the QCLs in the 3.8-4.1 micron band to being only a small fraction of those of the QCLs in the 4.6-5 micron band. Therefore, in order to significantly increase the CW power and wall-plug efficiency of 3.8-4.1 micron-emitting QCLs, compared to those so far obtained from conventional-design QCLs, it is the goal of this program to develop new active-region designs, similar to the shallow-well [Ref 4], the step-taper-active structure [Ref 5], or other innovative structures that will deliver temperature insensitive and CW output power device performance in the 3.8-4.1 micron wavelength range that is comparable to lasers operating in the 4.6 to 5 micron band. It is also the goal of this program to demonstrate greater than 1,000 hours laser lifetime performance. If active cooling of the laser is necessary, cooling using thermal-electric cooler technology for room temperature operation is highly preferable. Work produced in Phase II may become classified. Note: The prospective contractor(s) must be U.S. Owned and Operated with no Foreign Influence as defined by DOD 5220.22-M, National Industrial Security Program Operating Manual, unless acceptable mitigating procedures can and have been implemented and approved by the Defense Security Service (DSS). The selected contractor and/or subcontractor must be able to acquire and maintain a secret level facility and Personnel Security Clearances, in order to perform on advanced phases of this contract as set forth by DSS and NAVAIR in order to gain access to classified information pertaining to the national defense of the United States and its allies; this will be an inherent requirement. The selected company will be required to safeguard classified material IAW DoD 5220.22-M during the advance phases of this contract. 

PHASE I: Design a QCL emitting in the 3.8-4.1 micron wavelength range at room temperature with 5 W minimum CW power, 15% minimum CW wall-plug efficiency, and nearly Gaussian beam with beam propagation ratio (M2) less than 1.5 showing a path to meeting Phase II goals. The Phase I effort will include prototype plans to be developed under Phase II. 

PHASE II: Optimize the QCL design from Phase I. Fabricate and fully characterize prototype QCLs in the 3.8-4.1 micron wavelength band with the minimum performance levels reached. Demonstrate a QCL prototype to meet all requirements. Demonstrate a QCL lifetime >1,000 hours with the performance criteria stated in Phase I. It is probable that the work under this effort may become classified under Phase II (see Description section for details). 

PHASE III: Fully develop and transition the high performance QCLs with the specifications stated in Phase II for DoD applications in the areas of Directed Infrared Countermeasures (DIRCM), advanced chemicals sensors, and Laser Detection and Ranging (LIDAR). The DoD has a need for advanced, compact, high performance MWIR QCL in Band IVA (3.8 – 4.1 micron) of which the output power can readily be scaled 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, and non-invasive health monitoring and sensing. 


1. Bai, Y., Bandyopadhyay, N., Tsao, S., Slivken, S. and Razeghi, M. “Room Temperature Quantum Cascade Lasers with 27% Wall Plug Efficiency.” Applied Physics Letters, 2011.

KEYWORDS: Quantum Cascade Lasers; QCL; Band IVA; Band IVB38 Micron; 41 Micron; Mid-wave Infrared; Continuous Wave 

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