The refractive index of nonlinear optical ionic crystal 4 ' -N,N-dimethylam
ino-N-methyl-4-stilbazolium tosylate (DAST) was controlled by a photobleach
ing technique. The ellipticity of the DAST refractive index ellipsoid decre
ased after the irradiation of a 532 nm laser. By means of the photobleachin
g effect we fabricated a grating on DAST single crystals by two-beam interf
erence. 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.