integrated optics

(optics) A thin-film device containing tiny lenses, prisms, and switches to transmit very thin laser beams, and serving the same purposes as the manipulation of electrons in thin-film devices of integrated electronics.

The study of optical devices that are based on light transmission in planar waveguides, that is, dielectric structures that confine the propagating light to a region with one or two very small dimensions, on the order of the optical wavelength. The principal motivation for these studies is to combine miniaturized individual devices through waveguides or other means into a functional optical system incorporated into a small substrate. The resulting system is called an integrated optical circuit (IOC) by analogy with the semiconductor type of integrated circuit. An integrated optical circuit could include lasers, integrated lenses, switches, interferometers, polarizers, modulators, detectors, and so forth. Important uses envisioned for integrated optical circuits include signal processing (for example, spectrum analysis and analog-to-digital conversion) and optical communications through glass fibers, which are themselves circular (or elliptical) waveguides. Integrated optical circuits could be used in such systems as optical transmitters, switches, repeaters, and receivers. See also Integrated circuits; Optical communications; Optical fibers.

The advantages of having an optical system in the form of an integrated optical circuit rather than a conventional series of components include (apart from miniaturization) reduced sensitivity to air currents and to mechanical vibrations of the separately mounted parts, low driving voltages and high efficiency, robustness, and (potentially) reproducibility and economy. As in the case of semiconductor integrated circuits, an integrated optical circuit might be fabricated on or just within the surface of one material (the substrate) modified for the different components by shaping structures (using etching, for example) or incorporating suitable substitutes or dopants, or alternatively, by depositing or expitaxially growing additional layers. It is also possible to construct independent components which are then attached to form the integrated optical circuit. This option, called hybrid, has the advantage that each component could be optimized, for example, by using gallium aluminum arsenide lasers as sources for an integrated optical circuit and silicon detectors. In the former case, the integrated optical circuit is called monolithic, and is expected to have the advantage of ease of processing, similar to the situation for monolithic semiconductor integrated circuits. Perhaps the most promising materials for monolithic integrated optical circuits are direct band-gap semiconductors composed of III–V materials such as gallium aluminum arsenide [(GaAl)As] and indium gallium arsenide phosphide [(InGa)(AsP)] since with suitable processing they may perform almost all necessary operations as lasers, switches, modulators, detectors, and so forth. See also Electrooptics; Laser; Optical modulators; Semiconductor heterostructures; Spectrum analyzer; Waveguide.

Combining electrical and optical components on the same silicon-based substrates used in the fabrication of a semiconductor chip. Also called "silicon photonics," fiber-optic communications employs numerous integrated optics devices, including lasers, photodetectors, beam splitters, isolators, filters, prisms, modulators and switches. See optoelectronic and photonic.

Download Computer Desktop Encyclopedia to your iPhone/iTouch