Sol–gel thin films for optics and photonics

Abstract

Thin films have wide applications in the area of optics and photonics. Conventional thin film processing is usually followed for deposition, but the sol–gel route is unique as it can be applied very easily in a cost effective way on desired substrates of any shape for specific applications. In this review, the basic optical designs of antireflection, high reflection, different types of optical filters, coloured coatings, etc. have been discussed with some typical examples of sol–gel products. The importance of coloured coatings and low thermal emissivity coatings on window glass has also been highlighted. In addition, the use of sol–gel processing for different types of film formation which are effective for photonic applications such as non-linearity in optics, ferromagnetism in transparent dilute magnetic semiconductors (DMS), generation of quantum dots as phosphor, grating coupler waveguide in optical sensors are discussed. The basic characterizations of a few sol–gel products which may be used for photonic applications have also been highlighted.