Enhancement of laser noise image based on photorefractive nonlinearity of lithium niobate crystals

Abstract Enhancement of laser noise image based on stochastic resonance process in lithium niobate crystals is studied theoretically and experimentally in this paper. A noise function based on the refractive change in crystal is proposed for the numerical simulation. The simulation results show that the presence of noise can induce the optical nonlinearity in lithium niobate crystals to change from self-defocusing to self-focusing. Under an appropriate noise intensity, the strongest stochastic resonance process can occur, resulting in restored the image signal submerged by noise eventually. There is a good agreement between the experimental and numerical results. When a single noise image is transmitting in a nonlinear crystal system, the stochastic resonance process is considered to be the result of the self-coupling between the scattered noise and the transmitted signal when the noise and signal are scattered simultaneously in the crystal. The research results in this paper can provide theoretical and experimental guidance for the early acquisition and post-processing of images containing inherent noise, and will promote the industrialization of noise information sensing technology largely.