Determination of the extinction coefficient of a weakly absorbing multilayer system

Abstract

Based on a measured peak transmittance of a narrow band filter, the extinction coefficients of weakly absorbing thin films in a multilayer system can directly be calculated. This is a new method used for determination of the extinction coefficients of thin films in a weakly absorbing multilayer system with very easy to do and very high precision. The absorbing expression in a weakly absorbing interference narrow band filter is deduced. The principle of determination of the extinction coefficient is illustrated and the precision of the calculated extinction coefficient in a Ta2O5/SiO2 filter used in a dense wavelength division multiplexing system is analyzed.