REFLECTION SPECTROSCOPY OF OPTICAL COATINGS

New procedures have been devised for studying small energy losses in optical coatings. The ability to have large electromagnetic fields of the desired distribution in a multilayer system is used to optimize single and multiple reflection spectroscopy for the characterization of thin layers and interphase regions. The analysis is based on Poynting's theorem for radiation absorption. Linearized equations are derived for these low-loss cases, and experimental setups for maximum sensitivity are discussed. It is shown how to reduce complex multiphase spectroscopic data to optical constants which represent material properties. It is shown how losses caused by one absorbing species can be analyzed in the presence of another. Both experimental and computer simulated data are analyzed. Typical data reducing procedures are given for mirror coatings, lens coatings, losses due to impurities throughout a film, and losses due to contaminants at a film phase boundary.