Tunable diffraction grating using ultraviolet-light-induced spatial phase modulation in dual-frequency liquid crystal

An electrically tunable diffraction phase grating using ultraviolet (UV)-light-induced spatial dielectric modulation of a dual-frequency liquid crystal (DFLC) cell is demonstrated. A photomask with transparent and opaque stripes was used for fabricating the grating. In the UV-exposed stripes, the negative dielectric anisotropy sD«d tolane compound of the DFLC mixture is partially polymerized resulting in a decreased threshold voltage as compared to that of the unexposed region. Upon applying a constant voltage, the phase difference between the adjacent pixels is produced. The first-order diffraction efficiency reaches ,60% which agrees well with the simulation results. Due to the dual-frequency addressing at 30 Vrms, the response time of the DFLC phase grating was measured to be ,1 ms at room temperature. © 2004 American Institute of Physics. [DOI: 10.1063/1.1781752]