High power, high efficiency quantum cascade laser systems for directional infrared countermeasures and other defense and security applications

Abstract

We present our latest results on the development of high power, high efficiency room temperature quantum cascade lasers. Strain-balanced, InP-based quantum cascade structures, designed for light emission at 4.6 μm using a new non-resonant extraction design approach, were grown by molecular beam epitaxy and processed as buried heterostructure lasers. Maximum single-ended continuous-wave optical power of 3 W was obtained at 293 K for devices with stripe dimensions of 5 mm by 11.6 μm mounted on diamond submounts. Corresponding maximum wallplug efficiency and threshold current density were measured to be 12.7% and 0.86 kA/cm². 7 mm-long, 8.5 μm-wide devices mounted on aluminum nitride submounts with optimized reflectivity coatings on the output facet emitted 2.9 W under the same conditions and 1.2 W in uncooled pulsed operation. Leveraging this research, we developed fully packaged, air-cooled, table-top turn-key laser systems delivering in excess of 2 W of collimated continuous-wave radiation. The high performance and level of device integration make these quantum cascade lasers the primary choice for various defense and security applications, including directional infrared countermeasures, mid-wave infrared illuminators and free space optical communications.