Improved switchable achromatic phase shifters

We present optimized designs for two switchable achromatic phase shifters u sing a pair of ferroelectric liquid-crystal devices with retardations of a half-wave mounted between two quarter-wave retarders. The first system can be used with a linearly polarized beam to introduce phase shifts of 0 degre es, 90 degrees, and 270 degrees, that are almost independent of the wavelen gth, over a wide range of wavelengths. The other system can tie used to int roduce phase shifts of 0 degrees and +/-120 degrees between two orthogonall y polarized beams. (C) 1999 Society of Photo-Optical Instrumentation Engine ers. [S0091-3286(99)00206-8].