AC electric field assisted photo-induced high efficiency orientational diffractive grating in nematic liquid crystals.

An orientational grating with reduced scattering noise is formed in fullerene-doped and undoped homeotropic nematic liquid crystal cells by simultaneous application of both spatially modulated light and ac electric field. The first-order diffraction efficiency obtained in the fullerene-doped cell reaches ~30 %, approaching the maximum value predicted by theory. Effective nonlinear index coefficient is ~0.9 cm2/W and ~1000 times larger than previous observations in C(60)-doped nematic liquid crystals using a dc field. Grating formation time can be as short as 1 s, which is ~100 times shorter than those found by us using a dc field and previous studies.