Fast Optical Switching Using Cyanine Dye-Doped Nematic Liquid Crystal

Two kinds of cyanine dye were doped respectively in 4-cyano-4'-pentylbiphenyl (5CB) at a concentration ca. 1.0 wt%, and the mixture was sandwiched between two pieces of rubbed glass plates. The third-order nonlinear optical responses of cyanine dye-doped 5CB layers were measured for light polarized parallel to the oriented direction by the resonant femtosecond forward degenerate four-wave mixing technique at 820 nm. The time resolution of the system was ca. 0.3 ps. The amplified spontaneous emission spectra of cyanine dye-doped 5CB layers indicate that the decay of the slow response was accelerated with increasing laser power. The population grating disappears within ca. 5 ps.