Two-photon induced polymer nanomovement.

We present the first report of two-photon induced plastic surface deformation in solid polymer films. Exposure of azo polymer films, which absorb in the visible range (lambda(max) = 480 nm), to intense 920 nm irradiation leads to polarization dependent photofluidic polymer nanomovement caused by photoselective two-photon trans <-->cis isomerization. The deformations were induced by a gradient of light intensity; and strongly depend on the wavelength and the polarization direction of the incident laser light and the position of the focused spot with respect to the plane of the polymer film.