Three-dimensional planarized diffraction structures based on surface relief gratings in azobenzene materials

The method of step-by-step formation of correlated 3D phase optical structures is presented. Surface relief gratings (SRG) recorded in azobenzene polymer layers are alternated with layers of a spacer polymer with a different refractive index. A pair of azobenzene and spacer polymers with excellent compatibility makes it possible to prepare layers of good optical quality in a stack without destruction of SRG in the previous layer. A correlated stack of six layers (three active and three spacer layers) with 2D structures of different types (linear, tetragonal, and hexagonal) were built. In this way hierarchical 3D structures with different grating periods or different shapes of SRG can be also produced, resulting in full flexibility of the structure type and grating parameters.