A Solution To the Adhesion Problem of Oxide Thin Films on Zinc Selenide Optical Substrates

Abstract

Zinc selenide optical substrates have high transparency within the 0.5- to 14.0-mu m wavelength range. This makes them an attractive candidate for multiband imaging applications in optical components. In order to minimize reflection loss in visible, near-infrared, and mid-infrared applications, zinc selenide lenses are coated with multi-layered oxide thin films by physical vapor deposition method or ion beam deposition. In this study, a four-layer anti-reflective filter at 1.064 gm and between 3.6 and 4.9 gm is applied to zinc selenide using an ion beam deposition system. The filter is used for a dual-beam optical application. The filter is composed of metal oxide layers that have an adhesion problem on zinc selenide. In order to solve this adhesion problem they were heat-treated at 300 degrees C for varying amounts of time prior to metal oxide coating. Treated samples were characterized in terms of their roughness, contact angle, morphology, refractive index, transparency, crystallography and chemical composition. Results show that it is possible to manufacture durable oxide thin film coatings on zinc selenide, by using a well-designed pre-treatment processes.