Optical power limiting with photoinduced anisotropy of azobenzene films

We study the power-limiting properties of photoanisotropic azobenzene films with low-power laser. The trans-cis photoisomerization and molecular reorientation of azobenzene molecules induced by polarized laser beams result in intensity-dependent anisotropic effects. Consequently, the transmittance of the input beam that passes through the film between two crossed polarizers becomes enhanced at low intensities and clamped at high intensities. The limiting threshold is adjustable by changing the intensity of excitation beam.