Near infrared nonvolatile holographic recording in doubly doped LiNbO 3 :Fe crystals

Abstract

Photorefractive crystals have been deeply studied for holographic data storage. A number of approaches have been studied to improve the storage properties of such materials. In particular, methods to make the photorefractive gratings nonvolatile, i.e., insensitive to erasure during readout and during storage in the dark, have been developed. Doubly doped lithium niobate crystals can realize nonvolatile holographic recording by a real time and all optical processing, which have become a topic of great current interest. Sensitive light with short wavelength, such as UV light, and recording light are simultaneously applied in the recording process, and only one recording beam is used in the fixing process. Previous researches of this kind of crystals are always based on 633nm red light or shorter wavelength recording light. Longer wavelength recording light are more applicable for a practical data storage system. In this paper, for the first time, near infrared nonvolatile holographic recording is realized in different kinds of doubly doped LiNbO 3 :Fe crystals. In our experiments, the same sensitive light and recording lights at different wavelengths are adopted to compare the recording performance. The recording conditions are optimized to improve the near infrared recording characteristics. In near-infrared two-center holographic recording, the intensity dependence of recording sensitivity is found to be different with that by recording at 633nm, caused by small bulk photovoltaic coefficient of Fe traps, long response time and the simultaneous erasure of recorded hologram by sensitizing light.