**Tsvetanka Babeva**

Institute of Optical Materials and Technologies "Akad. J. Malinowski", Bulgarian Academy of Sciences, Akad. G. Bonchev str., bl. 109, 1113 Sofia, Bulgaria; babeva@iomt.bas.bg; Tel.: +359-2-979-3502

Received: 11 November 2020; Accepted: 18 November 2020; Published: 23 November 2020

**Abstract:** This Special Issue is devoted on design and application of thin films and structures with special emphasis on optical applications. It comprises ten papers, five featured and five regular papers, authored by respective scientists all over the world. Diverse materials are studied and their possible applications are demonstrated and discussed: transparent conductive coatings and structures from ZnO doped with Al and Ga and Ti-doped SnO2, polymer and nanosized zeolite thin films for optical sensing, TiO2 with linear and non-linear optical properties, organic diamagnetic materials, broadband optical coatings, CrWN glass molding coatings and silicon on insulator waveguides.

**Keywords:** transparent conductive coatings; optical sensing; broadband design; linear and non-linear optical properties; sidewall roughness; organic diamagnetic materials
