Abstract

The goal of the deposition of layers in a thin film optical coating is to achieve a reproducible result from each coating run. Various film thickness monitoring techniques may be used. The author generally favors the monitoring of the optical thickness since an optical result is what is desired. Some designs such as narrow bandpass filters are mostly dependent on the optical thickness, and others such as beamsplitters are also quite dependent on the index of refraction of the layers. If accurate knowledge of the real photometric level of transmittance or reflectance of the coated part is available from the optical monitor during the deposition of homogeneous layers, both the optical thickness and the index of refraction, and thereby the physical thickness, can be calculated.

© 1998 Optical Society of America