PHASE MODULATION CHARACTERISTICS ANALYSIS OF OPTICALLY-ADDRESSED PARALLEL-ALIGNED NEMATIC LIQUID-CRYSTAL PHASE-ONLY SPATIAL LIGHT-MODULATORCOMBINED WITH A LIQUID-CRYSTAL DISPLAY

An optically addressed parallel-aligned nematic-liquid-crystal spatial light modulator (PAL-SLM) has been studied as a dynamic phase-only li ght modulation device. The phase modulation characteristics of the PAL -SLM using a liquid crystal display (LCD) as an addressing mask were i nvestigated by analyzing diffraction efficiencies resulting from binar y gratings projected from the LCD. A more than 2 pi phase-only modulat ion depth was achieved. The highest first-order diffraction efficiency of approximately 38% was also obtained; this is close to the theoreti cal limit. The experimental results of diffraction efficiencies depend ing on the phase modulation depth are in good agreement with the simul ation for the system operation.