Surface emitting quantum-cascade ring laser

Quantum-cascade lasers with surface emission of radiation by means of a grating formed in the upper waveguide cladding layers by ion-beam milling are fabricated and studied. The active region of the laser heterostructure is based on the In$_{0.53}$Ga$_{0.47}$As/Al$_{0.48}$In$_{0.52}$As alloy alloys and uses a design with two-phonon resonance emptying of the lower level in the cascade. Room-temperature lasing near 7.9 $\mu$m is demonstrated for a laser with a ring-cavity diameter of 191 $\mu$m. The mode spacing in the lasing spectra corresponds to whispering-gallery modes.