Introduction

Thin-film multilayer coatings are applied to optical elements and structures to increase their functionality and modify optical performance [1]. Multilayer coatings incorporate the properties of the individual thin- film layers to achieve new or improved optical performance, which is not possible from each individual layer. They typically consist of alternating layers of high, intermediate, and low refractive index materials. Thin metal layers are also used. Layer thicknesses depend on the spectral characteristics required, and typically range from 50 A to 5000 A. The deposition of a conductive dual-band high reflector coating is described here. The coating is applied to a variety of curved and flat windows, and is used to reflect two wavelength bands, transmit in a near infrared wavelength band, and to heat and deice the optical window. The coating is deposited by RF and DC reactive magnetron sputtering, and consists of fourteen layers of titanium dioxide (TiO₂), silicon dioxide (SiO₂), silicon nitride (Si₃N₄), and a conductive silver (Ag) layer.