Comprehensive study of antireflection coatings for mid-infrared lasers

Abstract

A comprehensive study is done for optimizing antireflection coatings at mid-infrared wavelengths around 3.4 μm for applications in semiconductor lasers. Different materials are tested for single and double layer coatings. The coatings are characterized by comparing the change in the threshold currents before and after coating the lasers. The change in the differential slope efficiency was used to estimate the loss in the coatings. The lowest value achieved for a single layer coating was 5% using aluminum oxide while a minimum value of reflectivity of 7 × 10−4 was achieved with a double layer coating of zinc selenide and silicon dioxide. The coatings' quality was tested using scanning electron microscopy and tape test. The study provides a comprehensive list of materials that can be used for antireflection coating applications in the mid-infrared region.

Simple and Compact Longitudinally Excited CO2 Laser Driven with A Fast High-Voltage Solid-State Switch

“…In the traditional way, single-or multilayer film coating technology is used to manipulate the high and low refractive indices [8][9][10]. However, multiple problem may arise after the film coating [11][12][13]. First, the optical properties of the coating may be damaged by dust, defects, humidity or other kinds of environmental degradations.…”