Stretched exponential kinetics for photoinduced birefringence in azo dye doped PVA films

Abstract

We fabricated azo dye (methylorange) doped poly vinyl alcohol (MO/PVA) thin films and measured the photoinduced birefringence (PIB) kinetics for several pump beam intensities and for various MO concentrations by using the pump-probe technique. A novel approach to explain the transient behaviors of the photoinduced anisotropy is presented by employing an empirical stretched exponential time response in the course of the trans–cis–trans photoisomerization of azo molecules and is compared with the experimental data, showing excellent agreement. The stretched exponent is estimated to be β=0.34±0.04, revealing amorphous nature of the MO/PVA system.