Dynamics of photoinduced second order nonlinearity in dimethylamino-nitrostilbene polymer thin films

All-optical encoding of macroscopic second order susceptibility in a dimethylamino-nitrostilbene (DANS) polymer thin film is demonstrated. We show that the main mechanism responsible for the induced nonlinearity in DANS polymer is the angular hole burning effect due to trans–cis isomerization as distinct from azo-polymers, in which considerable reorientation of trans-molecules occurs. The DANS sample exhibits better dark stability in comparison with azo-systems such as disperse red 1 polymethylmethacrylate (DR1–PMMA). The results are explained by the absence of thermal cis–trans relaxation in DANS–PMMA.