Femtosecond-laser induced formation of grating structures in planar polymer substrates

Grating structures are fabricated in polymer substrates by femtosecond-(fs-)IR-laser radiation. Several sorts of polymer are employed as polymeric basic material for the grating manufacture: polymethylmethacrylate (PMMA), fluorinated PMMA, poly-N-methyl methacrylimide (PMMI), polycarbonate (PC), polyimide (PI) and polysiloxane. Surface and volume gratings are fabricated by positioning the focus of the fs-laser beam directly on the surface or inside the volume of the polymeric substrate, so by the right choice of the irradiation parameters the irradiated zone of the substrate is ablated, modified or carbonized. The sample is moved according to a scanning algorithm in order to generate the grating structure. The diffraction efficiency of the grating samples is measured by a HeNe laser. Some proposals are given for the mechanism of the grating generation.