Abstract

Filters based on the interference of light in thin films are, no doubt, the most versatile of all spectral filters. Not only do they permit a very close control of the spectral characteristics of incident radiation, but they do so over a range of wavelengths extending from the x-ray to the sub-millimeter region. However, their performance is to a large extent governed by the optical constants of the materials available for their construction. There are spectral regions in which there is a lack of suitable materials and there the performance of filters based on thin film coatings is very rudimentary. Optical thin film filters also have an undesirable dependence on the angle of incidence of the radiation and are not suitable for the control of radiation over extended spectral regions. Furthermore, depending on the process used for their manufacture-, the performance of optical multilayer filters may change in time.

© 1992 Optical Society of America