Abstract

Applying the principles of nonlinear optics for 3D data storage holds much promise in the context implementing an optical memory device that would be capable to store large data arrays. The possibility to use two-photon transitions in photochromic materials for this purpose was discussed and experimentally investigated in recent studies [1 - 3]. In this paper, we analyze a scheme for 3D optical data storage where data writing is performed through two-photon transitions resulting in photochromic coloring in the material. It is demonstrated that the use of a frequency-tunable laser provides the opportunity to appreciably increase the efficiency of photochromic transformations and, thus, to reduce the energies of light beams involved in the process of data writing. We analyze the advantages of two-photon optical storage schemes using laser beams with different frequencies over those using a single laser beam. We discuss the results of experimental studies devoted to two-photon coloring in photochromic materials and analyze the possibility of optimizing power and geometric parameters of the optical scheme for two-photon data writing. It is demonstrated that the cross section of two-photon absorption in a photochromic material can be completely described in terms of components of the cubic-susceptibility tensor of a medium, which provides an opportunity to apply the principles of nonlinear optics, including the technique of polarization measurements, for understanding the dependence of the cross section of two-photon absorption on the polarizations of light waves involved in the process of photocoloring.

© 1996 Optical Society of America