Binary-phase zone-plate arrays based on hybrid solgel glass

An organically modified silane zirconate-based solgel material is used for the fabrication of binary-phase zone-plate arrays. The synthesized hybrid s olgel material has a negative tone under UV exposure and can be patterned b y a UV-lithography process. The transmittance of the material is nearly 100 %, and the refractive index is 1.52. Two different diffractive lens arrays with focal lengths of 5 and 42 cm have been fabricated. The average roughne ss of the zone surface is less than 20 nm. The diffraction efficiencies of the lens arrays are measured as a function of modulation depth and exposure dose. A diffraction efficiency of 30% is achieved. (C) 1998 Optical Societ y of America.