New optics - new materials

The nature and applications of optical materials have evolved rapidly in re cent years. Their role as passive optical elements in free space has been a ugmented by so-called photonic systems. These can have many active componen ts-oscillators, amplifiers, frequency converters, modulators, switches, rou ters and so on-most of which rely, to some degree, on optical field confine ment. The design of appropriate materials for this new technology involves progress on two separate levels. There is a need both for the optimisation of microscopic electronic properties and for the separate control of bulk o ptical parameters on the scale of optical wavelengths. This article uses se veral examples to illustrate selected areas of current activity under both these headings. It also emphasises the need for more general methods for cr eating optical scale microstructure.