We describe the design, fabrication, testing, and performance of a two
-layer free-standing beam splitter for use in far-infrared Fourier tra
nsform infrared spectrometers. This bilayer beam splitter, consisting
of a low-index polymer layer in combination with a high-index semicond
uctor layer, has an efficiency that is higher than that of the best co
mbination of four single-layer Mylar beam splitters currently in use f
or spectrometry from 50 to 550 cm(-1). (C) 1996 Optical Society of Ame
rica