Three-dimensional optical memory

Abstract

A novel 3-D optical memory device is presented which has the potential of storing extremely high (~1013-bits/cm3) bit densities. The information may be accessed randomly and in parallel by utilization of two beams which overlap inside the medium allowing volume optical information storage. The 3-D memory device is based on two-photon writing, reading, and erasing of information in a photochromic material embedded in a polymer matrix. An infrared beam and a visible beam combined induce a structural change on the photochromic material which corresponds to the write cycle. Subsequent to that, the initially transparent molecule absorbs in the visible and can be read by a combination of two near-infrared beams. The observed fluorescence, which is induced by the two-photon absorption of the infrared beams, constitutes the read signal. Erasing of the imprinted information can be achieved by warming the molecule with two infrared beams on which the molecule reverts to the original unwritten structural form. The written information persists for many days at dry ice temperatures (−78°C).