Formation of negative-index-change waveguide lenses in LiNbO(3) by using ion milling

We report, for the first time to our knowledge, fabrication of two types of negative-index-change waveguide lens in LiNbO(3) by using ion milling. The first type is an analog Fresnel lens formed by grooves milled into the waveguide. The second is a hybrid lens that combines analog Fresnel zones in the central region with chirp gratings on the sides formed by the same means. We have obtained simultaneously high-efficiency and near-diffraction-limited focusing characteristics in both types of lens. The ion-milling technique employed should be capable of producing similar lenses in any other waveguide substrate, such as GaAs.