Update on the development of high performance anti-reflecting surface relief micro-structures

Abstract

Microstructures built into the surfaces of an optic or window, have been shown to suppress the reflection of broad-band light to unprecedented levels. These antireflective (AR) microstructures form an integral part of an optic component, yielding an AR property that is as environmentally robust, mechanically durable, and as radiation-hardened as the bulk material. In addition, AR microstructures built into inexpensive glass windows, are shown below to exhibit a threshold for damage from high energy lasers of nearly 60 J/cm2, a factor of 2 to 4 increase over published data for conventional thin-film dielectric material AR coatings. Three types of AR surface relief microstructures are being developed for a wide variety of applications utilizing light within the visible to very long wave infrared spectrum. For applications requiring broad-band operation, Motheye AR textures consisting of a regular periodic array of cone or hole like structures, are preferred. Narrow-band applications such as laser communications, can utilize the very high performance afforded by sub-wavelength structure, or SWS AR textures that consist of a periodic array of simple binary, or step profile structures. Lastly, Random AR textures offer very broad-band performance with a simple manufacturing process, a combination that proves useful for cost sensitive applications such as solar cells, and for complex devices such as silicon and HgCdTe sensor arrays. An update on the development of AR microstructures is discussed for many specific applications. Data from SEM analysis, reflection and transmission measurements, environmental durability testing, and laser damage testing, is shown for AR microstructures fabricated in silicon, fused silica, borofloat glass, ZnGeP, AMTIR, As2Se3, As2S3, and GaAs.