Asymmetrical dual-cavity filters and their application to thickness uniformity monitoring

The use of asymmetrical dual-cavity (ADC) fi lters with two transmittance peaks is proposed for a simultaneous monitoring of the thickness uniformities of high- and low-index materials. The method described works independently of the manufacturing technique used, and can detect non-uniformities of refractive indices. The properties of these ADC fi lters are studied using Smith's concept of effective interfaces, and admittance diagrams. An experimental application of this method is demonstrated, which can be used for increasing the yield of manufactured optical fi lters.