Introducing atomic layer epitaxy for the deposition of optical thin films

Atomic layer epitaxy (ALE) is introduced for the preparation of dielectric multilayer structures for optical applications. Owing to the self-limiting growth process, arising from alternate saturating surface reactions, ALE possesses several features which make it an attractive technique for depositing optical thin films: simple and accurate thickness control, uniformity over large-area substrates, good reproducibility and straightforward scale-up. In the present work, ALE deposition of some basic optical components, i.e. antireflection and high-reflection coatings, neutral beam splitters and Fabry-Perot filters, is demonstrated using ZnS and Al2O3 as high and low refractive index materials. The optical performance of the resulting components was examined by comparing the measured transmittance and reflectance spectra with those calculated for the ideal structures. In addition, other ALE processes which are of potential use in the preparation of optical dielectric multilayers are summarized briefly. The drawbacks of ALE are discussed as well.