Norihiro FUKUCHI, YE Biqing¹, Yasunori IGASAKI², Narihiro YOSHIDA², Yuji KOBAYASHI² and Tsutomu HARA

Central Research Laboratory, Hamamatsu Photonics K.K., 5000, Hirakuchi, Hamamatsu, Shizuoka 434-8601, Japan
¹State Key Laboratory of Modern Optical Instrumentation, Zhejiang University, Hangzhou, Zhejiang 310027, China
²Electron Tube Division #2, Hamamatsu Photonics K.K., 314-5, Shimojinzo, Iwata, Shizuoka 438-0193, Japan

(Received July 22, 2005; Accepted July 29, 2005)

We have developed optically-addressed and electrically-addressed liquid crystal spatial phase-only light modulators having no pixelized structures. We obtained a large depth of phase-only modulation and high diffraction efficiency based on the electro-optical characteristics of a parallel-aligned nematic liquid crystal. These spatial light modulators (SLM) are of the reflection type, so there would be a loss of power in the readout light from the half mirror, which was set up so as to separate the incident and reflected lights. To optimize the characteristics of a reflection type spatial phase-only light modulator, we have proposed an oblique incident optical readout setup. We have examined the effect of conditions such as the polarization direction and the incidence angle of the readout light, and the orientation of liquid crystal molecules in the SLM. High diffraction efficiency close to the theoretical maximum value was obtained by adjusting the above conditions. The simulation analysis can well explain the experimental results of phase modulation.

Key words: spatial light modulator, phase modulation, liquid crystal, diffraction efficiency, oblique incident readout