Formation of a buried lateral density grating in azobenzene polymer films

A density grating buried under a smooth surface is reported for an azobenze ne-containing polymer film. The grating is formed by annealing a polymer sa mple pre-inscribed with a surface grating for several hours above T-g, crea ting a lateral density difference on the order of 10 %. It is shown that th e rate of the process can be influenced by the intensity and polarization o f the probe laser. Growth of photoinduced liquid-crystalline aggregates is proposed as the most probable explanation for the observed behavior.