Optical coatings by ion-beam sputtering deposition for long-wave infrared quantum cascade lasers

The authors report on the development of high-reflection and multilayer antireflection coatings using ion-beam sputtering deposition for long-wave infrared (λ∼9.4μm) quantum cascade lasers. A metallic high-reflection coating structure using Y2O3 and Au is demonstrated to achieve a high reflectance of 96.70%, and the use of a multilayer anti-reflection coating structure using PbTe and ZnO is demonstrated to achieve a very low reflectance of 1.64%. A 170% improvement of peak laser output power and a 169% increase in wall-plug efficiency are reported without any beam steering effects.