Longitudinal sensitivity of the photoinduced molecular migration in azobenzene-containing films

The effect of field component perpendicular to the surface (longitudinal fields) on the photo-induced molecular migration and surface deformations in azobenzene polymer films are investigated. Case of tip-enhanced near-field illumination of the polymer surface is first discussed. In order to rule out the possible influence of mechanical interaction between tip and polymer, tightly focused higher-order laser beams are then used. We demonstrate that the surface topography is principally induced by longitudinal fields. Our findings can be explained by the translational diffusion of isomerized chromophores when the constraining effect of the polymer-air interface is considered.