The influence of dimensional parameters of DAST nanocrystals on their linear and nonlinear optical parameters

Nonlinear optical trans -4'-(dimethylamino)-$N$-methyl-4-stilbazolium tosylate (DATS) nanocrystals are synthesized in polymethylmethacrylate by nucleation in a drying polymer film at different solvent concentrations. Nanocrystals with sizes progressively increasing from 70 to 2500 nm are obtained. The effect of size on the nonlinear optical coefficient is studied by generation of the second harmonic of a 1064-nm Nd:YAG laser. It is shown that the nonlinear optical coefficient decreases with decreasing crystal size by no more than a factor of 1.5. The optical absorption spectra and the shape of nanocrystals are studied as functions of their size.