White light micrograting multiplexing for high density data storage

Abstract

Recording of multiplexed microholographic gratings with improved recording volume for high density optical data storage is proposed and demonstrated. By using a hybrid diffractive-refractive objective lens with extended depth of focus, we have achieved a recording beam size of approximately 1 microm and a focal depth of 20 microm. Multiple gratings corresponding to spectral lines within the 400-650 nm spectral band have been successfully multiplexed in a single recording spot or pit of size 1.25 microm on a DuPont photopolymer film using a white light source along with narrowband filters or dispersion elements, thus demonstrating the storage of multiple bits in a single pit. Simultaneous readout of multiple bits in a single storage pit is accomplished with a microspectrometer-type readout head using a white light source.