Photobleaching of submicron DAST crystals in a PMMA film by direct laser writing

Selective photobleaching of DAST ( trans -4'-(dimethylamino)-Nmethyl-4-stilbazolium tosylate) non-linear crystals in a 2-$\mu$m-thick polymethacrylate film using direct laser writing at a wavelength of 532 nm at a power of 1–10 mW and a recording speed of 5–35 $\mu$m/s is studied. The laser pattern is established as a function of recording parameters. The destruction of crystals and their transition into the amorphous state enabled one to record a structure that is well resolved in the optical microscope and in the luminescence signal. No layer surface violation at the crystal damage sites is detected. The method ensures the formation of a grating with a periodic modulation of the nonlinearly optical coefficient, which is essential in the quasi-phasematching generation.