@article{JelkenHenkelSanter2019,
  author    = {Jelken, Joachim and Henkel, Carsten and Santer, Svetlana},
  title     = {Solving an old puzzle: fine structure of diffraction spots from an azo-polymer surface relief grating},
  series = {Applied physics : B, Lasers and optics},
  volume    = {125},
  journal   = {Applied physics : B, Lasers and optics},
  number    = {11},
  publisher = {Springer},
  address   = {Heidelberg},
  issn      = {0946-2171},
  doi       = {10.1007/s00340-019-7331-8},
  pages     = {11},
  year      = {2019},
  abstract  = {We report on the experimental and theoretical interpretation of the diffraction of a probe beam during inscription of a surface relief grating with an interference pattern into a photo-responsive polymer film. For this, we developed a set-up allowing for the simultaneous recording of the diffraction efficiency (DE), the fine structure of the diffraction spot and the topographical changes, in situ and in real time while the film is irradiated. The time dependence of the DE, as the surface relief deepens, follows a Bessel function exhibiting maxima and minima. The size of the probe beam relative to the inscribed grating (i.e., to the size of the writing beams) matters and has to be considered for the interpretation of the DE signal. It is also at the origin of a fine structure within the diffraction spot where ring-shaped features appear once an irradiation time corresponding to the first maximum of the DE has been exceeded.},
  language  = {en}
}
@article{JelkenSanter2019,
  author    = {Jelken, Joachim and Santer, Svetlana},
  title     = {Light induced reversible structuring of photosensitive polymer films},
  series = {RSC Advances},
  volume    = {9},
  journal   = {RSC Advances},
  number    = {35},
  publisher = {RSC Publishing},
  address   = {London},
  issn      = {2046-2069},
  doi       = {10.1039/C9RA02571E},
  pages     = {20295 -- 20305},
  year      = {2019},
  abstract  = {In this paper we report on photoswitchable polymer surfaces with dynamically and reversibly fluctuating topographies. It is well known that when azobenzene containing polymer films are irradiated with optical interference patterns the film topography changes to form a surface relief grating. In the simplest case, the film shape mimics the intensity distribution and deforms into a wave like, sinusoidal manner with amplitude that may be as large as the film thickness. This process takes place in the glassy state without photo-induced softening. Here we report on an intriguing discovery regarding the formation of reliefs under special illumination conditions. We have developed a novel setup combining the optical part for creating interference patterns, an AFM for in situ acquisition of topography changes and diffraction efficiency signal measurements. In this way we demonstrate that these gratings can be "set in motion" like water waves or dunes in the desert. We achieve this by applying repetitive polarization changes to the incoming interference pattern. Such light responsive surfaces represent the prerequisite for providing practical applications ranging from conveyer or transport systems for adsorbed liquid objects and colloidal particles to generation of adaptive and dynamic optical devices.},
  language  = {en}
}