Modelling, Fabrication and Optimization of Anti-reflective coatings Designed for Mid-infrared Quantum Cascade Lasers

In this work, we have described numerical simulations and experimental fabrication of three different anti-reflection (AR) coatings optimized for mid-infrared Quantum Cascade Lasers (QCL's). We proposed a novel coating made of a double-layer structure obtained from silicon dioxide and silicon nitride, dielectric materials that are completely compatible with the technological QCL's fabrication process. Proposed double-layer AR coating was compared with two other AR coatings known from the literature. Each coating has been designed to reduce reflectivity from the front laser mirror from 27 % to similar to 10 %. The proposed AR structures can be used in the spectral range of 2.5- 6 mu m. Due to the use of the proposed double-layer coating, it was possible to obtain the desired reflectivity while reducing the total coating thickness by 100 nm.