Lithographic fabrication of diffractive optical elements in hybrid sol-gel glass on 3-D curved surfaces

We demonstrate the lithographic fabrication of diffractive optical elements (DOEs) in hybrid SiO2/TiO2 sol-gel glass on 3-D curved surfaces. The concentric circular gratings with periods of 20 μm, 10 μm and 5 μm have been fabricated in sol-gel glass on concave lens by laser direct writing successfully. Continuous 3-Dimensional surface relief with a height of 435 nm, 110 nm and 50 nm has been obtained for the period of 20 μm, 10 μm and 5 μm respectively. The optical test results of the fabricated DOE shows only a little bit deviation from the theoretical calculated results which can be explained by 3-D curved surface effect. We believe this technology can be an effective method to fabricate DOEs with even more complex surface profile on 3-D curved surfaces in terms of its simplicity and cost-effectiveness.