New midwave infrared laser sources for defense and security needs

摘要

Strain-balanced, InP-based quantum cascade laser structures, designed for light emission at 4.6 μm using a new non-resonant extraction design approach, were grown by molecular beam epitaxy. Removal of the restrictive two-phonon resonance condition, currently used in most structure designs, allows simultaneous optimization of several structure parameters influencing laser performance. Following the growth, the structure was processed to yield 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. Corresponding maximum wallplug efficiency and threshold current density were measured to be 12.7% and 0.86 kA/cm2. Fully packaged, air-cooled lasers with the same active region/waveguide design and increased laser core doping delivered approximately 2.2 W in collimated beam. The high performance and level of device integration make these quantum cascade lasers the primary choice for various defense applications, including directional infrared countermeasures, infrared beacons/target designators and free space optical communications.