N151-023 TITLE: Low-Cost-By-Design Widely Tunable Mid-Wave Infrared Surface Emitting Lasers

TECHNOLOGY AREAS: Air Platform, Chemical/Bio Defense, Electronics

ACQUISITION PROGRAM: JSF-MS

OBJECTIVE: Develop a low-cost, robust, compact, widely tunable surface-emitting (SE) semiconductor laser with no mechanical moving parts of any kind. The device development in this program should enable significant performance improvement over the current incumbent mid-wave infrared (MWIR) semiconductor laser technology. More importantly, this program will enable game-changing wafer-level fabrication and testing for the MWIR tunable lasers to substantially reduce the cost of manufacturing by design and hence the affordability of the lasers.

DESCRIPTION: Quantum cascade lasers (QCLs) are being steadily incorporated into current and future Navy applications such as directional infrared countermeasure (DIRCM) and other surveillance mine and improvised explosive device sensing applications. In particular, the DIRCM performance could be substantially improved by the use of high-power widely tunable mid-wave infrared (MWIR) QCLs with excellent beam quality, which can defeat the future-generation missile infrared (IR) seeker head with laser-jamming wavelength-blocking countermeasures. However, serious performance and reliability gaps exist in commercially available external-cavity tuned QCLs [1, 2] that can prevent them from transitioning onto military platforms. These issues include high sensitivity to shock and vibration; high temperature variations of the precision optical alignment of all the external optical elements and mechanical moving parts; high manufacturing cost of the entire hybrid assembly of QCL and external optics; and, the inherently slow tuning speed due to required mechanical movement of grating for tuning. Current Navy research efforts are focusing on developing a completely monolithic, edge-emitting QCL solution with extremely wide wavelength tunability, high CW output power, and excellent beam quality

Monolithic SE MWIR QCLs hold promise for significant advantages over their edge-emitting counterparts in terms of both reliable operation and manufacturing cost. Recent reliability studies have shown that edge-emitting QCLs� failure modes are triggered by the QCLs� high facet optical-power densities and/or temperatures which, in turn, generally limit the reliable output power of edge-emitting QCLs. The Navy is also working on developing SE non-tunable QCLs to circumvent the reliability drawbacks of edge-emitting QCLs. More importantly, one of the Navy�s goals is also to significantly improve the affordability of the MWIR QCLs. The cost reduction of the SE QCLs is primarily achieved via the elimination of a few high-cost, low-yield, labor intensive fabrication and packaging steps such as wafer lapping, cleaving, dicing, facet coatings, and chip bonding, etc., which amount to 60 to 75% of the total cost of manufacturing the edge-emitting QCLs.

The device developed as a result of this SBIR should enable significant performance improvement over the current incumbent MWIR semiconductor laser technology. More importantly, successful technology development will enable game-changing wafer-level fabrication and testing for the MWIR tunable lasers to substantially reduce the cost of manufacturing by design and hence the affordability of the lasers.

Each of the above-mentioned Navy efforts is on track to deliver each of its performance, affordability, and reliability objectives. Because of the unique affordability advantage of the SE QCLs and the performance and reliability benefits of the monolithic tunable QCLs, it is the goal of this SBIR to combine the best of both technologies to develop a low-cost-by-design, widely tunable MWIR SE QCL with unique, unparalleled combination of unprecedented high affordability, performance, and reliability.

PHASE I: Develop and prove feasibility of a viable, robust, and manufacturable design for a single widely tunable SE QCL with a room-temperature CW output power > 1 W over the entire tunable range at least �12% from a center wavelength around ~4.6 micron with near diffraction-limited beam quality (M2 < 1.5). A viable design path forward for further increasing the output power of the SE tunable laser operating at CW mode at room temperature scheme should be proposed and included as part of the deliverable for Phase I.

PHASE II: Fabricate, demonstrate, and deliver a prototype of widely tunable SE QCL with output emission out of a single aperture with output power > 5 W CW and outstanding beam quality (M2 < 1.5) over the entire tunable range at least �12% from a center wavelength around ~4.6 micron. Further demonstrate a viable path forward to power-scale the tunable SE QCL monolithically at the wafer level without external optics to power levels exceeding 20 W CW while maintaining M2 < 1.5. It is critical to incorporate manufacturing cost reduction as part of the design criteria throughout all the design phases in all phases of this program.

PHASE III: Fully develop and transition the widely tunable SE QCL for Department of Defense (DoD) application in the areas of DIRCM, advanced chemical sensors, LIDAR, and commercial applications.

PRIVATE SECTOR COMMERCIAL POTENTIAL/DUAL-USE APPLICATIONS: The commercial sector can significantly benefit from this technology development in the areas of detection of toxic industrial gases, environmental monitoring, and non-invasive medical health monitoring and sensing.

REFERENCES:
1. Caffey, D., et al. (2011). Recent results from broadly tunable external cavity quantum cascade lasers. Presentation 7953-54. Paper presented at the International Society for Optics and Photonics, Photonics West 2011, San Francisco, California. doi: 10.1117/12.875093

2. Hugi, A., et al. (2009). External cavity quantum cascade laser tunable from 7.6 to 11.4 um. Appl. Phys. Lett., 95, 61103.

KEYWORDS: Sensing; Qcl; Tunable; High Power; DIRCM; surface emitting

** TOPIC AUTHOR (TPOC) **

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