Design and fabrication of self-compensating ZnSe beam splitter in LWIR region

Abstract

The design and fabrication of a self-compensating beam splitter in the Long-wave infrared (LWIR) wavelength range is discussed in the article. The self-compensating plate beam splitter finds its application in a passive Fourier Transform Infrared (FTIR) system for the detection of chemical warfare clouds from a distance of up to a few kilometers. The beam splitter was designed for the LWIR wavelength band of 8.0–12.0 µm, with a beam splitting ratio of 50:50, i.e., for 50% transmission and 50% reflection @ 45° angle of incidence (AOI). The zinc selenide (ZnSe) based beam splitter was developed using an ion-assisted e-beam evaporation technique. A Perkin Elmer FTIR spectrometer was used to measure the average transmission/reflection of 50:50 in the 8.0–12.0 µm wavelength band. The fabricated beam splitter complied with MIL-F-48616 environmental tests with no visible damage to the coated optics. The fabricated ZnSe self-compensating beam splitter was integrated in the Michelson interferometer set-up and the interferogram is recorded.