Phase-shift error as a result of molecular alignment distortions in a liquid-crystal point-diffraction interferometer

We report the observation of nematic director distortions around the diffra cting element of a liquid-crystal point-diffraction interferometer. The obs erved director field distortions are similar to those reported in the liter ature for other liquid-crystal guest-host systems. We show how the alignmen t distortion changes as a function of the voltage applied to the liquid-cry stal cell, leading to an observed phase-shift error. Tailoring of surface a nchoring conditions and judicious choice of phase-shift algorithm can impro ve device accuracy. (C) 2000 Optical Society of America OCIS codes: 120.818 0, 120.5050, 160.3710, 220.4840, 280.3720, 160.1190.