Thin film filter performance for extreme ultraviolet and x-ray applications

Substantial work has been done to characterize filter materials for the vacuum ultraviolet and x-ray regions of the electromagnetic spectrum. This paper summarizes the theoretical basis for predicting performance and compiles the results of different measurement programs for comparison. Recent work that better quantifies transmission as a function of wavelength for various filter and window materials is reported. Other applications of thin films in which these optical properties are important include photocathodes and x-ray laser targets. Of particular interest are figures giving linear absorption coefficients as a function of wavelength for commonly used filter materials. Also included are recent data on the effect of aging on aluminum filters, plus test data and comments on the use of composite materials designed to adjust the bandpass of a filter to meet particular research requirements. The data are presented so that the reader may more easily design and predict the performance of filters and windows for specific applications.