TECHNOLOGY AREA(S): Air Platform

ACQUISITION PROGRAM: PMA 272 Tactical Aircraft Protection Systems

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 5.4.c.(8) 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: Develop a modular approach based on two-dimensional quantum cascade laser arrays to scale the average power level of MWIR laser sources beyond 200 Watts, while allowing beam combining to maximize brightness.

DESCRIPTION: Important military applications that include infrared (IR) countermeasures and scene illumination can benefit from high-power laser sources operating in the MWIR and the long-wave infrared (LWIR).  Quantum Cascade Laser (QCL) technology offers a path for a high-power, cost-effective and low-space, weight, and power (SWaP) solution.  Recent progress led to the demonstration of single QCL emitters reaching multi-Watts output power in continuous wave (CW) while maintaining wall-plug efficiency exceeding 15%.  Scaling the power level to tens of Watts and beyond is currently being explored using approaches based on linear QCL arrays and various beam combining schemes.

The field of high-brightness semiconductor lasers has been dominated by edge-emitting laser technology until recently, when two-dimensional arrays of vertical-cavity surface emitting lasers (VCSELs) emerged as a promising alternative [Refs 1, 2].  The latter approach focuses on achieving high power by having high-density arrays, which reduces the need to obtain high power from each element and allows optimization of individual laser efficiency.  This has a number of other advantages that include (1) low manufacturing costs because of large-scale, wafer-level fabrication, test, and burn-in, (2) ease of packaging and straightforward integration with two-dimensional micro-optics, mostly because the position of individual emitters is set very accurately using lithography, (3) high reliability because of the low power required per element, and (4) low speckle because of the large number of element emitting independently.  Furthermore, heat spreading and cooling is generally more efficient for a heatsink with a planar geometry compared to multiple thin and densely-packed heatsinks.

The main goal of this SBIR topic is to develop a MWIR QCL source based on a cost-effective architecture similar to that of high-power, two-dimensional VCSEL arrays.  However, because of the polarization selection rules of intersubband transitions in III-V materials, QCLs cannot make use of a laser cavity along the growth direction, as in near infrared VCSELs, but alternative means such as using angled end-facet mirror or surface emission gratings to enable surface emission, exist.  These include for example lasers with second-order gratings or edge emitters with integrated mirrors directly etched into the semiconductor.  The proposed approach would preferably be based on a single, monolithic chip but a more modular strategy is also acceptable.  Other areas of focus for this project will be to optimize the drive conditions as well as the power and efficiency of each array element in order to reach unprecedented overall average power levels exceeding 200 Watts during CW.  Innovative thermal management solutions that would eliminate the need for active water cooling are strongly preferred.  A beam combining scheme maximizing the brightness of the source needs to be included.

PHASE I: Design and demonstrate feasibility of an innovative concept based on two-dimensional, vertical-emitting QCL arrays for scaling the output power of MWIR laser source beyond 200 Watts in CW or QCW mode.  The proposed approach needs to include the modeling of (1) beam combining optics maximizing the brightness of the laser source while maintaining an output beam as close as possible to the diffraction limit and (2) a detailed thermal management solution requiring no use of water cooling.  The Phase I effort will include the development of prototype plans for Phase II.

PHASE II: Fabricate and test a prototype based on the design and simulation results developed during Phase I.

PHASE III DUAL USE APPLICATIONS: Fully develop and transition the high-power, two-dimensional arrays for DoD applications in the areas of directional infrared countermeasure (DIRCM), advanced chemicals sensors, and light detection and ranging (LIDAR).  The DoD has a need for advanced, compact, robust two-dimensional MWIR QCL array of which the output power can readily scaled via beam combining for current- and future-generation DIRCMs, LIDARs, and chemicals/explosives sensing.  The commercial sector can also benefit from the crucial, game changing technology development in the areas of detection of toxic gases, environmental monitoring, and non-invasive health monitoring and sensing.

REFERENCES:

1. Moench, H. et al. "High-power VCSEL systems and applications." Proc. SPIE 9348, High-Power Diode Laser Technology and Applications XIII, 93480W (March 13, 2015). http://proceedings.spiedigitallibrary.org/proceeding.aspx?articleid=2206439

2. Zhou, D. et al. "Progress on vertical-cavity surface-emitting laser arrays for infrared." Proc. SPIE 9001, Vertical-Cavity Surface-Emitting Lasers XVIII, 90010E (February 27, 2014). https://www.researchgate.net/publication/262983952_Progress_on_vertical-cavity_surface-emitting_laser_arrays_for_infrared_illumination_applications

KEYWORDS: Laser Array; QCL; Quantum Cascade Laser; Mid-Infrared; Beam Combining; Aircraft Protection