Metal Oxide Thin Films for Advanced Photonic Applications

Oxide materials represent a versatile and fundamental platform for photonics, allowing the manipulation of light through optical property engineering. This review focuses mainly on the physics and applications of simple oxides, analysing their use in the realisation of dielectric mirrors, in particular of distributed Bragg reflectors, and planar microcavities. Critical aspects regarding the design of multilayer structures, the control of optical confinement and the improvement of the quality factor in passive devices are discussed. However, to provide a complete picture of the evolution of the field, the section dedicated to oxide materials anticipates future directions dominated by complex oxides such as lithium niobate, lithium tantalate and barium titanate required for active photonics. In this context, a necessary technological paradigm shift is highlighted: the transition from the current use of film-on-insulator platforms to the direct epitaxial growth of these functional materials, an essential step for the scalability and monolithic integration of future photonic devices.