N121-032 TITLE: Low-Cost, Robust, Monolithic Semiconductor Mid-Infrared Laser With Very Wide Tunability

TECHNOLOGY AREAS: Air Platform, Chemical/Bio Defense, Sensors, Battlespace

ACQUISITION PROGRAM: PMA 272

OBJECTIVE: Develop a low-cost, robust, compact, monolithic chip-based solution for a quantum cascade laser (QCL) with no mechanical moving parts of any kind, high continuous wave (CW) output power, excellent beam quality, and very wide tunability in the mid-wave infrared (MWIR) spectral range.

DESCRIPTION: High-power, monolithic, cost-effective, and reliable semiconductor MWIR laser sources, such as QCLs operating in the CW regime on thermoelectric coolers (TECs) [Lyakh et al. (2009) see reference section], are highly desirable and critical for current and future Navy applications. These applications include directional infrared countermeasure (DIRCM) and other surveillance and mine- and improvised explosive device- (IED)-sensing applications. In particular, DIRCM performance can be substantially improved by using high-power widely tunable MWIR QCLs with excellent beam quality, which can defeat future-generation missile IR seeker head with a laser-jamming wavelength-blocking countermeasure. This is a unique topic that seeks the best-in-class, game-changing, scientifically and technologically innovative, widely tunable mid-infrared (IR) laser solutions for Future Naval Capability (FNC) Sea Shield Missile Defense and Joint Strike Fighter (JSF) programs.

Commercially available external cavity-tuned (ECT) QCLs with relatively reasonable output power levels and impressible tunable ranges as wide as �14.5 percent tunability from the center wavelength [Hugi et al. (2009) and Caffey (2011)] have been recently demonstrated for sensing and instrumentation applications in laboratory settings and civilian operating environments [Pushkarsky et al. (2006) and Van Neste et al. (2009)]. However, there are serious performance and reliability gaps in ECT QCLs that can potentially prevent them from transitioning into military platforms. First, ECT QCL requires hybrid integration and mechanical movement of external optical elements for wavelength tuning. Hence, the optical alignments of all the elements are sensitive to shock, vibration, and extreme temperature variations, thereby resulting in ECT configurations that are not sufficiently robust for reliable operation in harsh military environments. Second, the entire hybrid assembly of external grating, optics, and mechanical parts adversely impacts the overall laser system�s size and weight and contributes to its high manufacturing cost. Third, wavelength tuning by mechanically moving the grating or mirror is inherently slow, thus prohibiting deployment in some applications that require very agile wavelength tuning over a very wide spectral range. Fourth, it is also difficult to achieve tuning over a broad spectral range free of mode hopping because ECT QCLs require very high-quality antireflection coatings with low reflectivity, and active and simultaneous adjustment of grating angle, EC length, and laser chip optical length. Finally, the ECT QCL's hybrid integration platform does not provide a viable path forward for more compact monolithic beam combining of the tunable lasers for future power scaling. It is therefore the goal of this program to seek a feasible solution for a low-cost monolithic tunable semiconductor-based MWIR laser source with very wide tunability that circumvents all the shortcomings of the existing ECT QCL platforms. It is also the intent of this call for proposals to seek a completely broadly tunable, monolithic semiconductor laser solution with high output power capability and excellent beam quality. Proposed tunable laser solutions must circumvent the previously mentioned shortcomings of existing ECT QCL platforms.

PHASE I: Design and develop a viable TEC-cooled, monolithic, widely tunable, single-mode QCL source with a room temperature (RT) CW output power of greater than 500 millawatt (mW) over the entire tunable range, at least �10 percent from a center wavelength around ~4.6 microns with near diffraction-limited beam quality (M2 of less than 1.3). The design should enable tunable step size as small as 0.1 nanometer (nm). Propose a viable design path forward for further increasing the output power of the laser operating at RT CW mode via an integrated on-chip power amplifier and/or monolithic beam combining scheme.

PHASE II: Demonstrate and deliver a prototype of a monolithic, widely tunable, single-mode QCL source with an RT CW output power of greater than 500 mW over the entire tunable range, at least �10 percent from a center wavelength around 4.6 microns with near diffraction-limited beam quality (M2 of less than 1.3) and tunable step size as small as 0.1 nm. Investigate and propose designs that would increase the tunable laser RT CW output to greater than 10 W.

PHASE III: Commercialize the monolithic, broad QCL wavelength tuning technology and leverage the advantages of wafer-level scalable manufacturing to develop a very cost-effective manufacturing process for technology transition to various system integrations for both DOD and civilian applications.

PRIVATE SECTOR COMMERCIAL POTENTIAL/DUAL-USE APPLICATIONS: The commercial sector can use advanced chemical sensors based on high-power, broadly tunable QCLs to detect toxic industrial gases and for environmental monitoring.

REFERENCES:
1. Caffey, D., et al. (2011). Recent results from broadly tunable external cavity quantum cascade lasers, Photonics West Presentation 7953-54. Retrieved from Daylight Solutions.

2. Hugi, A., et al. (2009, August). External cavity quantum cascade laser tunable from 7.6 to 11.4 �m, Appl. Phys. Lett., 95, 061103, doi:10.1063/1.3193539

3. Lyakh, A., et al. 3 W continuous-wave room temperature single-facet emission from quantum cascade lasers based on nonresonant extraction design approach, Appl Phys. Lett., 95, 141113, doi:10.1063/1.3238263

4. Pushkarsky, M., et al. (2006, July). Sub-parts-per-billion level detection of NO2 using room-temperature quantum cascade lasers, PNAS, 103, 10846, doi:10.1073/pnas.0604238103

5. Van Neste, C. W., et al. (2009, March). Standoff spectroscopy of surface adsorbed chemicals, Analytical Chemistry, 81(5), 1952-1956, doi:10.1021/ac802364e

KEYWORDS: Quantum Cascade Lasers, Monolithic, Tunable, High Continuous Wave Output Power, Mid-Wave Infrared, Beam Quality

** TOPIC AUTHOR (TPOC) **

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