3D structures using surface relief gratings of azobenzene materials

Abstract

We present here a method of step-by-step 3D structure fabrication using holographic formation of surface relief gratings (SRG) in azobenzene-containing layers alternated with spacer layers. The method possesses opportunities that could not be realized by other holographic approaches, especially the variation of grating periods or the shape of the SRG in different layers (hierarchical structures), full flexibility of the structure type and parameters. One of the main problems to be solved is the compatibility of active azobenzene-containing polymers and a material for the spacer layers. We resolved the problem and found active and spacer polymers with excellent compatibility. The materials allow the preparation of films with good optical quality and the inscription of SRG with modulation amplitudes up to 1 µm in reasonable time. The refractive index difference between active and spacer polymers (currently 0.15–0.2) results in appreciable diffraction efficiency of the SRG after the application of the spacer layer. The phase correlation technique between adjacent layers has been developed. The fabrication of multilayer structures has been demonstrated by examples of a combination of linear, tetragonal and hexagonal SRG with three active layers and hierarchical structures.