Quantum Cascade Surface Emitting Lasers

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 mu m is achieved. Finally, single-mode emission with a side-mode suppression ratio larger than 33 dB is demonstrated for a 248 mu m short cavity, which is mounted with the epitaxial layer up and operated in continuous wave at 20 circle C$<^>{\circ}{\rm C}$. In this work, the Quantum Cascade Surface Emitting Laser (QCSEL) is introduced. This mid-infrared laser, producible in high volumes at low cost, leverages wafer-level testing and exploits miniaturization to minimize the electrical power dissipation. The obtained results for wavelengths near 4.5 and 8 mu m pave the way to the broad adoption of the QCSEL in optical sensing applications. image