Beam fanning effect and image storage in Ce: KNSBN crystal

Abstract

A non-synchronously-numerating experimental system is applied in this research. The effect of the incident beam intensity I and the beam incident angle θ on beam fanning effect is investigated with a singular beam incident on Ce:KNSBN crystal. The results show that the beam fanning effect strongly depends on I and θ. The threshold effect of I for the beam fanning in Ce:KNSBN crystal is observed, and the threshold intensity of incident beam keeps the same value of 38.2 mW/cm 2 for different θ, and the steady beam fanning intensity I fsat reaches a peak at θ=15° under the same I. In addition, the effect of the incident beam modulated on the beam fanning noise and holographic storage in Ce:KNSBN crystal is studied. And the results suggest that the beam fanning noise is effectively suppressed, and the quality of the reappearance image is greatly improved.Ce:KNSBN crystal, beam fanning effect, threshold characteristic, image storageThe beam fanning effect, which can be observed in almost all photorefractive crystals, strongly impedes the progress of holographic volume storage in high-gain photorefractive crystals. Recently, the beam fanning in LiNbO 3 crystal is minutely studied. Liu et al. [1] proposed that the intensity of beam fanning in LiNbO 3 crystal was toned up by doping with Fe element; Zhang et al. [2] believed that the beam fanning effect of LiNbO 3 :Fe crystal could be suppressed by doping with Mg ion; Zhang et al. [3] reported that the intensity threshold of the beam fanning of LiNbO 3 :Fe crystals could be reduced by doping with damage-resistant dopants (Mg 2+ , Zn 2+ , In 3+ ). Currently, the beam fanning effect in doping KNSBN has been elementarily researched, too. Residori et al. [4] investigated the dynamic process of the beam fanning effect in Cu:KNSBN crystal at different c axis; Ramazza et al. [5] considered that the resolving power of two waves coupling volume grating was strongly effected by the beam fanning; Zhang et al. [6] made use of the ordinary component of the pump beam as an incoherent beam to erase the fanning in Ce:KNSBN, and the gain of two waves coupling was enhanced; Guo et al. [7] researched the fanning effect on the dynamics of two waves coupling in Ce:KNSBN crystal. However, the problems that the quality of the holographic storage is damaged by the beam fanning noise, etc. were not resolved as yet. In this research, the beam fanning effect as functions of the incident beam intensity and beam incident angle was studied with 532 nm beam incident on Ce:KNSBN crystal, and the beam fanning noise and holographic storage in Ce:KNSBN crystal were investigated, in the case where beam is modulated, and the corresponding explanations are given.