The production of Fresnel lenses in sol-gel derived Ormocers by holography

Abstract

Micro Fresnel lenses were prepared from photosensitive organic-inorganic nanocomposites of the Ormocer-type by irradiation of films of 10 µm in thickness with an interference pattern of two laser beams, mixing a planar reference wavefront and a spherical object wavefront. To monitor the polymerization behavior of the organic groups during irradiation under real time conditions, a characterization method was developed to study changes in optical thickness n d by measuring changes of index of refraction and shrinkage during polymerization. Three-dimensional Fresnel structures were obtained by removing the unpolymerized areas by a solvent. Variation of index of refraction can also be obtained by diffusion of monomers in regions of higher light intensity. A model, similar to the Colburn-Haines model is presented.