Fully symmetric nulling beam combiners

Appl Opt. 2001 Apr 1;40(10):1668-71. doi: 10.1364/ao.40.001668.

Abstract

A simple method of nulling broadband light is presented. A mirror-symmetric pair of right-angle periscopes is first used to introduce a geometric field flip between two incident light beams, after which the light is combined by means of one of a number of constructive two-beam interferometers. A reciprocal pair of beam-splitter passages provides for complete symmetry. Such an approach greatly eases beam-splitter design requirements and should find use both in initial ground-based nulling experiments and ultimately in space-borne interferometers targeted at direct extrasolar planet detection.