Fabrication of surface relief optical elements in ternary chalcogenide thin films by direct laser writing

Direct laser writing with a continuous-wave high intensity and over-band gap laser is applied to realize surface relief optical elements in ternary As-S-Se and Ge-As-S thin chalcogenide films. The topology of created structures in dependence on the experimental conditions is investigated. Analyses indicate that the formation mechanisms of the surface patterns are thermally induced processes generated by the local heating and involve thermoplastic deformation, mass flow induced by the surface tension gradient and evaporation. Diffractive gratings with a period of 2.56 µm, depths of up to 100 nm, and different periodic surface structures were patterned at the surface of 1 µm thick films. The spectral dependencies of diffraction efficiency were measured and discussed.