Coatings with induced transmission.

A brief review is given of how fundamental concepts of thin film optics (potential transmittance, the two-effective-interfaces theorem, the principle of equivalent layers, matching conditions and absentee layers) are used to design optical coatings with controlled absorptance. The general principles are illustrated by a discussion of interference filters containing both dielectric and metallic layers, including the design and preparation of induced transmission filters. Reference is also made to coatings for optimizing the photon efficiencies of photodetectors. Further insight into how coatings with absorbing layers function is provided by consideration of the electric field distribution of radiation within the coatings.