The goal of integrated optics (IO) is to develop miniaturized optical devices of high functionality on a common substrate. The state-of-the-art of integrated optics is still far behind its electronic counterpart. Today, only a few basic functions are commercially feasible. However, there exists a growing interest in the development of more and more complex integrated optical devices.
In IO we distinguish between optical integrated circuits, which perform functions similar to electronic circuits in communications systems, and planar optical devices, which are integrated optical systems other than communication systems.
Optical integrated circuits
Researchers hope to put wave guides, modulators, switches, and other active optical functions onto various substrates. It is visualized that thin films and micro-fabrication technologies can suitably be adopted to realize optical counterparts of integrated electronics for signal generation, modulation, switching, multiplexing and processing.
In optical integrated circuits, light is confined in thin film wave guides that are deposited on the surface or buried inside a substrate. Glasses, dielectric crystals and semiconductors can be used as substrate materials. The functions that can be realized depend on the type of substrate used. Researchers are challenged to identifying materials which have both the right electro-optical properties and a reliable means of forming them into useful structures on the integrated circuit. Unfortunately, many current-generation materials that are used to fabricate monolithic optical devices have high attenuation and therefore high transmission losses.