Quantum Cascade Surface Emitting Lasers

Abstract

A low-cost single frequency laser, emitting in the mid-infrared spectral region and dissipating minimal electrical power, is a key ingredient for the next generation of portable gas sensors for high-volume applications involving chemical sensing of important greenhouse and pollutant gases. Herein, a Quantum Cascade Surface Emitting Laser (QCSEL) is proposed, which is implemented as a short linear cavity with high reflectivity coated end-mirrors to suppress any edge emission and employs a buried semiconductor diffraction grating to extract the light from the surface. By wafer-level testing, the cavity length scaling is investigated, mirror reflectivities larger than 0.9 are extracted, and a pulsed threshold power dissipation of 237 mW for an emission wavelength near 7.5 µm is achieved. Finally, single-mode emission with a side-mode suppression ratio larger than 33 dB is demonstrated for a 248 µm short cavity, which is mounted with the epitaxial layer up and operated in continuous wave at 20 (Formula presented.).