Two-Photon Optical Storage in Photorefractive Polymers in the Near-Infrared Spectral Range

Abstract

We report the use of a polymer-based photorefractive material for three-dimensional bit optical data storage using near-infrared illumination. The research was conducted using photorefractive materials that were fabricated in two polymer matrices: poly(N-vinylcarbazole) (PVK) and poly(Methyl Methacrylate) (PMMA). The recording samples also consisted of the following compounds in various proportions: 2,5-dimethyl-4-(p-nitrophenylazo)anisole (DMNPAA), 2,4,7-trinitro-9-fluorenone (TNF) and N-ethylcarbazole (ECZ). Two-photon excitation was used as the recording mechanism to achieve rewritable bit data storage in a photorefractive polymer. As a result of two-photon excitation, the quadratic dependence of the excitation on the incident intensity produces an excitation volume that is confined to the focal region in both the transverse and axial directions. The use of ultrashort pulsed lasers, while effective, is not a practical solution for an optical data storage system. This research demonstrates the ability to produce three-dimensional rewritable bit data storage using continuous-wave illumination. Using this technology it has been possible to achieve a density of 88 Gbits/cm³, which in the future could be increased to 3.5 Tbits/cm³.