Multilayer recording holographic data storage using a varifocal lens generated with a kinoform

A multilayer recording method using a varifocal lens generated with a kinoform is presented. In this recording method, a focus position is axially displaced by adding a defocus phase to a phase modulation pattern, which consists of a random phase mask and a computer-generated reference pattern. Shift selectivity and multiplexed recording are experimentally investigated in coaxial holographic data storage. Experimental results show that the proposed method allows the recording of holograms along an optical axis without any mechanical movement.