Abstract

A high-index dielectric slab can be coated on one face with a low-index thin film of quarterwave optical thickness at oblique incidence so that it reflects monochromatic light as a halfwave retarder and refracts it without change of polarization. The other (exit) face of the slab is coated with a bilayer that produces total refraction of light also without change of polarization. When this coated slab is used as a beam splitter (BS) in a Michelson interferometer, it renders its operation completely independent of source polarization. A specific example is presented of a coated Ge-slab BS for 10.6-μm radiation and 45° angle of incidence. Such a BS is tolerant to film-thickness errors and is reasonably achromatic over a small (10–11-μm) wavelength range.

© 1986 Optical Society of America