Properties of optically addressed liquid crystal spatial light modulators studied by Mach-Zehnder interferometry

In this work optically addressed liquid crystal spatial light modulators are experimentally investigated. Local reorientation of molecules in the modulator and local changes of effective refractive index n(eff) (x,y) are induced by modulated light intensity I (x,y). We present preliminary results of measurements of phase shifts in optically addressed liquid crystal panels using a Mach-Zehnder interferometer. Experiments were performed for the panels filled with nematic and dye-doped nematic liquid crystals. Optical addressing was realized by Ar+ laser beam (lambda = 514.5 nm) while the reading beam was supplied by He-Ne laser (632.8 nm). The operation voltage was in the range 4 - 20 V. The total phase shift under the influence of addressing light for the studied systems was 2 - 6 pi, sensitivity to the addressing light similar to muW/cm(2) per 2pi phase change and speed of response to the light was 20 ms - 30 s with total recovery time 0.5 - 120 s.