ABSTRACT
A dual-frequency liquid crystal based optical switch with orthogonally photo-patterned alignments is designed and fabricated. The cell gap is theoretically optimized for high switching performance. The measured extinction ratio of first diffraction order is over 20 dB with a low electric field of 3 V/µm. The switch On-Off time are measured to be 350 µs and 600 µs, respectively, both of which have reached submillisecond scale. Moreover, the switch is polarization independent, which has been predicted theoretically and further proved experimentally. This design is suitable in wide applications requiring fast response and polarizer free properties.
ABSTRACT
A diffraction grating is proposed by periodically defining the liquid-crystal director distribution to form alternate parallel aligned and twist nematic regions in a cell placed between two crossed polarizers. Based on the combined phase and amplitude modulation, both 1D and 2D tunable gratings are demonstrated. Low voltage ON/OFF switching of 1st order diffracted light with extinction ratio over 80 is achieved within a small voltage interval of 0.15 Vrms. Unique four-state feature of the cell is obtained and their applications in optical logic devices are discussed.
