Poled polymer thin-film gratings studied with far-field optical diffraction and second-harmonic near-field microscopy

Electrical poling induces polar ordering of molecules in a grating that has been holographically inscribed on a thin film of polymer with azobenzene side chains. The resulting χ(2) grating, seen by second-harmonic-generation (SHG) near-field scanning optical microscopy, can have a periodic structure that is significantly different from the topographical image. The far-field linear and SHG diffraction patterns correlate well with the grating structures. Poling of the thin-film grating, which presumably has photodriven nonuniform material properties within each period, leads to the more complex structure of the χ(2) grating.