Using scanning near-field microscopy to study photo-induced mass motions in azobenzene containing thin films

Abstract

Scanning near-field optical microscopy (SNOM) is used to study the photo-induced deformation of layered structures containing azobenzene derivatives. This approach is particularly relevant since it allows detecting in real-time, with the same probe the surface topography and the optical field distribution at the nanoscale. The correlation between the local light pattern and the ongoing photo-induced deformation in azobenzene-containing thin films is directly evidenced for different light polarization configurations. This unveils several fundamental photodeformation mechanisms, depending not only on the light field properties, but also on the nature of the material. Controlling the projected electromagnetic field distribution allows inscription of various patterns with a resolution at the diffraction limit, i.e. of a few hundreds of nm. Surface relief patterns with characteristic sizes beyond the diffraction limit can also be produced by using the nearfield probe to locally control the photo-mechanical process. Finally, the photo-mechanical properties of azo-materials are exploited to optically patterned metal/dielectric hybrid structures. Gratings are inscribed this way on thin gold films. The characteristic features (enhancement and localization) of the surface plasmons supported by these noble metal structures are studied by near-field optical microscopy.