Refractive index control and grating fabrication of 4'-N,N- dimethylamino-N-methyl-4-stilbazolium tosylate crystal
The refractive index of nonlinear optical ionic crystal 4 ' -N,N-dimethylamino-N-methyl-4-stilbazolium tosylate (DAST) was controlled by a photobleaching technique. The ellipticity of the DAST refractive index ellipsoid decreased after the irradiation of a 532 nm laser. By means of the photobleaching effect we fabricated a grating on DAST single crystals by two-beam interference. The calculation based on the diffraction efficiency indicates that the depth of refractive index change can be extended to 5.75-7.38 mum by 2.08 W/cm(2) irradiation power. This result is promising for the fabrication of DAST waveguides; by photobleaching.