SOME PROPERTIES OF ABSORBING BEAM-SPLITTERS

The equality of the reflected and transmitted irradiances by an unsupported metallic beam splitter is considered. An approximate analytical expression for the film thickness which ensures this condition for the parallel and perpendicular polarizations is given. The phase difference between the two output fields is expressed as a function of the optical parameters of the film. This phase difference departs substantially from pi/2, which is obtained from energy conservation in a lossless beam splitter.