More-dimensional surface-relief gratings in films of azo dyes

Abstract

Evaporated films of the azo-material DR 1 have been investigated. In the as-grown state partly crystalline films with low transmittance are obtained. Using homogeneous exposure transparent regions may be formed. The recording of holographic gratings in thin films (< 1 μm) of the azo dye is investigated for the case of more-dimensional light-intensity patterns. The mechanism of the photo-isomerisation of the azo-compounds is used to form dual gratings with a refractive index grating and a surface-relief grating. The grating-formation is investigated in case of 1D-gratings first. The time dependent diffraction efficiency is discussed in a model of 2 processes with different time-constants. A material transport process is involved in the formation of relief patterns. The enhancement of the modulation-depth of the surface-relief gratings is investigated for the application of a Corona discharge and a thermal treatment after the holographic recording. 2D-gratings are formed using either a 3-beam holographic set-up or a consecutive method. The resulting light patterns are simulated. Diffraction patterns and AFM-measurements are used to confirm these simulated structures. The modulation of the surface-relief gratings can be enhanced by thermal treatment after the holographic recording.