N211-022 TITLE: High Performance Continuous Wave Quantum Cascade Lasers Immune to Output Facet Optical Damage
RT&L FOCUS AREA(S): Directed energy; Quantum Science
TECHNOLOGY AREA(S): Air Platforms
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: Develop high-performance large output aperture mid-wave infrared (MWIR) Quantum Cascade Lasers (QCLs) with a large laser catastrophic optical damage threshold, thereby eliminating QCL failures due to the optical facet damage.
DESCRIPTION: Reliable Quantum Cascade Lasers (QCLs) capable of delivering 10 Watts continuous wave (CW) optical power [Ref 1] with high efficiency are of great interest to the Navy for various naval applications. Current generation devices with continuous wave (CW) output power over 3 Watts generally have a poor long-term reliability. Post-mortem analysis of failed high-power QCLs typically shows catastrophic output facet damage. The damage is strongly correlated with the peak optical intensity at the output facet. A game-changing solution is needed to enable the high-performance QCLs to have long-term reliability and meet/exceed the MILSPEC requirements [Ref 2].
An effective, innovative approach to solving the laser optical damage problem is to reduce optical power density at the output laser facet. For a fixed output power level, this can be attained by judiciously increasing the output aperture size without affecting the diffraction-limited beam quality. This can be achieved by employing a second-order distributed feedback (DFB) configuration where optical output is collected from either the surface or the substrate side of the device, as opposed to the edge of the laser. In this case the output aperture is three orders of magnitude larger than that for edge-emitting QCLs, thereby improving the catastrophic optical damage threshold by more than 1,000 fold. An additional advantage of second order DFB QCLs is that they can be pre-screened on the wafer-level, leading to labor and material saving cost benefits associated with cleaving and testing substandard edge-emitting QCL devices. Also, packaging of surface-emitting devices on submounts is less demanding due to their increased alignment tolerance. Therefore, QCLs with large output aperture and reduced optical power density can provide a significant reduction in price per watt for high power CW QCLs.
Although second order DFB QCLs were demonstrated over a decade ago, their performance significantly lags that for Fabry-Perot devices [Refs 3, 4]. In most explored DFB configurations, the grating interacts with the guided mode along the entire laser cavity. This unavoidably leads to additional optical losses, increasing laser threshold and reducing slope efficiency. This is especially detrimental to CW QCL operation.
This SBIR topic seeks the development of a novel QCL configuration that effectively leverages improvements in CW power and efficiency achieved for state-of-the-art Fabry-Perot QCLs, while at the same time offering the unparalleled reliability advantage due to a significant increase in output aperture size. The final device configuration should be compatible with a large-throughput, low-cost production, and therefore should not involve epi-growth interruptions. The specifications of the CW QCLs should have a large output aperture size no smaller than 1 millimeter(mm) x 10 micrometers (�m), CW efficiency higher than 20% and output power level higher than 20 Watts delivered in a nearly diffraction-limited beam with M2 < 1.5.
PHASE I: Design, document, and demonstrate feasibility of high performance CW QCLs with a large output aperture size (no smaller than 1mm x 10�m). Demonstrate, using numerical modeling, that projected CW efficiency exceeds 20% and output power level exceeds 20W delivered in a nearly diffraction limited beam with M2 < 1.5. Ensure that the approach shows that projected fabrication cost for new devices does not exceed that for state-of-the-art commercial buried heterojunction QCLs. In the Phase I Option, if exercised, carry out proof-of-concept experiments. The approach should show that projected fabrication cost for new devices, does not exceed that for state-of-the-art commercial buried heterojunction QCLs. The Phase I effort will include prototype plans to be developed in Phase II.
PHASE II: Construct, develop, and demonstrate the prototype devices based on the design from Phase I. Test and continually improve QCL performance while demonstrating CW efficiency and power to meet topic requirements. Demonstrate that the QCL devices can operate at full power for over 10,000 hours.
PHASE III DUAL USE APPLICATIONS: Fully develop, fabricate, test, and transition the technology based on the design and demonstration results developed during Phase II for DoD applications in the areas of Directed Infrared Countermeasures (DIRCM), advanced chemicals sensors, and Laser Detection and Ranging (LIDAR). The commercial sector can benefit from this crucial, game-changing-technology development in the areas of detection of toxic gas environmental monitoring, noninvasive health monitoring and sensing, and industrial manufacturing processing.
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KEYWORDS: Quantum Cascade lasers; QCL; optical facet; reliability; optical damage; Fabry-Perot; continuous wave