The sol-gel process for realisation of optical micro-structures in glass

We have applied the sol-gel process to generate optical microstructures in glass using in-house developed sol-gel materials. The synthesis of our sol-gel glass materials is based on the formation of particles of controlled size from organo-metallic compounds. The overall shrinkage during annealing of the gel material is negligible and does not imply crack formation. Silica, titania and binary oxides of silica titania oxide sol-gel materials have been used. A two-step pattern transfer is employed to replicate the structure in glass: first a polydimethylsiloxane (PDMS) replica is obtained from a Si, polymethylmethacrylate (PMMA) or polyimide (PI) master structure, and secondly, a layer of sol-gel material is applied on the PDMS 'soft-replica' to get diffractive micro-/nano-structures in glass after drying and annealing. These structures are characterised. by a scanning electron microscope (SEM) and by an optical diffraction setup.