Reading and writing of information in a frequency domain optical memory using GaAlAs diode lasers

Abstract

Recently there has been considerable interest in frequency domain optical memories based on the cryogenic phenomenon of photochemical hole burning.1 This phenomenon occurs whenever persistent photochemical changes can be induced by exposure to narrowband optical radiation tuned to a frequency within the inhomogeneously broadened zero phonon line of a photoactive material contained In a host. The narrowband radiation selectively excites that fraction of molecules whose homogeneous linewidth overlaps the excitation frequency. The ensuing photochemical reaction results in a persistent narrow dip or hole in the line shape. Since typical ratios of inhomogeneous- to-homogeneous widths are of the order of 103, 103 resolvable holes can be burned into the inhomogeneous line at each spatial location in the sample. Thus the storage density in such a frequency domain optical memory might ultimately be 103 higher than in a conventional optical memory. © 1983 Optical Society of America