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

Pao-Tai Lin; Xiao Liang; Hongwen Ren; Shin-Tson Wu
August 2004
Applied Physics Letters;8/16/2004, Vol. 85 Issue 7, p1131
Academic Journal
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 (Δε) 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.


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