Fabrication of GRIN-lenses by contactless electrophoretic-gradient formation in transparent nanocomposites

Abstract

A new approach to effective radial gradient refractive index (GRIN) lenses has been developed. It is based on the electrophoresis of ZrO2 nanoparticles with surface charges (ζ-potential) in a solvent free organic-inorganic hybrid matrix, synthesized from dodecandioldimethacrylate (DDDMA), methacryl silane (MPTS) and a complex of zirconium n-propylate (ZR) with methacrylic acid (MA). A DC-electric field of 2000 V/cm is applied by a set of ring electrodes on top and bottom of a cylindrical mould containing the matrix sol. The refractive index profile is measured in situ as a function of time by interferometry. The refractive index profile can be conserved by photopolymerization of the matrix. The resulting refractive index profiles are calculated by computer simulation based on electrophoretical diffusion theory and they are measured by real time Mach-Zehnder Interferometry. The parabolic refractive index gradient of the lenses obtained by variation of concentration of ZrO2 is in very good agreement with the result of computer simulation. By this method, it is possible to obtain 1 cm radial GRIN lenses with a Δn = 0.07 within 5 h.