Optical testing of infrared materials and components

The current status of in-house characterization and testing of IR materials and components is described. A range of techniques are described, which were developed largely to evaluate the ZnS produced at BAe, but are equally applicable to other mateirals intended for use in the 8-14 micron waveband. Measurement techniques are described for determining the transmission, refractive index, dn/dT, refractive index homogeneity, and the modulation transfer function (MTF). These are based around a Twyman-Green interferometer using a CO2 laser as the radiation source with the exception of the MTF measurement, which is done using Lateral Shearing Interferometry at the single wavelength of 10.6 microns. An in-house test facility has been constructed which allows all of these measurements to be carried out on a system based around the Twyman-Green arrangement with add-on sections to accommodate the test and component under examination. 9 references