In situ measurement of liquid crystal spatial light modulators' beam steering characteristics during gamma irradiation

Recent interest in liquid crystal spatial light modulators as a potential replacement to traditional optical beam steering methods have engendered experiments to determine the technology's resistant to gamma radiation such as may be encountered in a space environment. We previously investigated the effects of exposure of liquid crystal devices to ionizing radiation to total dose levels consistent with a 14-year mission at geostationary orbits (GEO). We reported on the parameters of retardation, contrast ratio and primary power current, which were monitored at various dosing intervals for liquid crystal cells and a spatial light modulator. Here we present for the first time measurements of spatial light modulators' beam steering characteristics taken while they are undergoing gamma irradiation. We examine data on angular deflection, intensity, and beam spread for the liquid crystal spatial light modulators obtained during irradiation. The modulators were in continuous operation during irradiation at approximately 23 Rad (Si)/s, and, again the total ionizing dose reached levels consistent with 14 years at GEO. We observed minimal to no degradation in performance, either from dose rate effects or from total ionizing dose, in these environments.