TECHNOLOGY AREAS: Air Platform, Sensors, Electronics, Battlespace

OBJECTIVE: Develop a power-scalable, robust, chip-based solution for a monolithic beam-combined quantum cascade laser (QCL) array with high continuous wave (CW) output power in the tens to hundreds of Watts and excellent beam quality in the mid-wave infrared (MWIR) spectral range for infrared countermeasure and other relevant DoD applications.

DESCRIPTION: High-power, monolithic, cost-effective, compact, and reliable MWIR laser sources operating in CW regime on thermoelectric coolers (TEC) are desirable and critical for current and future Navy applications, such as directional infrared countermeasure (DIRCM), and other surveillance and sensing applications. Individual QCLs emitting at ~ 4.6 micron with 3 Watts CW output power and wall-plug efficiency close to 15% have been recently demonstrated [1]. A possible method to increase the aggregate output power level of the laser sources while simultaneously maintaining near-diffraction-limited beam quality, is to combine multiple laser beams using coherent beam combining (CBC) or spectral beam combining (SBC) [2]. Most or all of today's CBC or SBC schemes demonstrated in the shorter wavelength ranges other than MWIR require hybrid integration of laser arrays with external optical elements and/or electronics, and hence a more cumbersome, costly and less reliable platform for demanding military field applications

It is the goal of this program to seek a power-scalable, chip-based platform that enables monolithic beam combining (MBC) of high-power CW QCLs. A complete MBC solution is sought that comprises a QCL array, QCL power amplifiers, and compact passive combiners that produce high-power outputs with excellent beam quality. Proposals on MBC of MWIR non-QCL semiconductor laser arrays will also be considered. Emission of the array�s aggregate wavelengths over a narrow wavelength range is very desirable. The capability to electronically tune all of the emission wavelengths of the entire monolithic laser array is also sought as this unique tuning capability will be very advantageous for various existing and future DoD applications, even though wide wavelength tunability is not a requirement in the current solicitation. It is also the intent of this program to seek a monolithic, power-scalable semiconductor laser platform with electronic tunability in wavelength. Any proposal on the laser array wavelength tunability that requires thermal tuning of the lasers or mechanical tuning elements such as those in external-cavity configurations will be considered non-responsive.

PHASE I: Demonstrate the feasibility of TEC-cooled, high power (greater than 15 Watts) QCL arrays at ~4.6 micron with a monolithically integrated MBC configuration resulting in a single output with M2 less than 1.5. Modeling must include the detailed integrated characteristics of the various passive and active optical elements, and the associated thermal management at the chip and the system level. A clear development path and plan describing how the power can be monolithically scaled to power levels between 50 to 100 Watts and how the devices can be economically fabricated with high production yield (greater than 10x of the current process) must also be provided.

PHASE II: Demonstrate and deliver a prototype compact CW QCL array with a monolithically integrated MBC configuration with more than 15 Watts of CW power over a narrow wavelength range centered around ~ 4.6 micron and M2 less than 1.5. Overall wall-plug efficiency of the overall MBC laser array solution must exceed 10%. Provide an assessment of manufacturing yield and product reliability of the monolithically integrated laser array solution.

PHASE III: Fully develop and transition the MBC CW QCL array for DoD application in the areas of DIRCM, advanced chemical sensors, and LIDAR.

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. Lyakh, A., Maulini, R., Tsekoun, A., Go, R., Patel, C. (2009). 3 W continuous-wave room temperature single-facet emission from quantum cascade lasers based on nonresonant extraction design approach. "Applied Physical Letters", 95, 141113.

2. Fan, T.Y., (2005). Laser beam combining for high-power, high-radiance sources. "IEEE Journal of Selected Topics in Quantum Electronics", 11(3), 567-577.

KEYWORDS: Mid-Infrared; Monolithic; Semiconductor; Beam Bombining; Laser Array; Quantum Cascade Laser (QCL)

Questions may also be submitted through DoD SBIR/STTR SITIS website.