USE OF 4 MIRRORS TO ROTATE LINEAR-POLARIZATION BUT PRESERVE INPUT-OUTPUT COLLINEARITY .2.

We report on the design, construction, and testing of a four-mirror re flective polarization rotator, proposed by Smith and Koch [J. Opt. Sec . Am. A 13, 2102 (1996)], that rotates by an angle phi the input linea r polarization while preserving the input-output beam collinearity. We correct errors in the previous work that led to an incorrect design f or a phi = pi/2 rotator. This type of pure rotator is simple and inexp ensive, and it is a direct application of the concept of the nonadiaba tic geometric phase to polarization rotation. We also present measurem ents of the polarization rotation for the case of three metallic mirro rs with antiparallel input and output beams, a test of geometric phase in polarization optics not done before. (C) 1997 Optical Society of A merica.