采用紫外光提高双掺杂铌酸锂晶体中全息记录的灵敏度和光栅强度

Improvement of Sensitivity and Refractive-Index Changes in Holographic Recording in Doubly Doped LiNbO_3 with UV Light

提出了一种在双掺杂铌酸锂晶体中用调制的双紫外光进行非挥发全息记录的方法。与通常的用紫外光敏化的非挥发全息记录相比,这种方法可以大幅度地提高光栅强度和记录灵敏度。联立双中心物质方程和双光束耦合波方程,数值分析了光栅强度和衍射效率随时间的变化并讨论了掺杂浓度和记录光强对紫外光非挥发全息记录机制下光折变效应的影响。研究发现,紫外光记录得到的深浅中心的光栅具有相同的相位,总的光栅(深浅中心光栅的叠加)强度为两光栅强度之和,固定过程中深中心的光栅得到增强;增大深浅中心掺杂的浓度可以提高光栅强度,增大记录紫外光的光强可以增加光栅的强度和记录灵敏度。理论模拟可以证实并预测实验结果。

A nonvolatile recording method with double modulated UV beams in （Ce, Cu）2 LiNbO3 crystals is proposed. Compared with the normal UV-sensitized nonvolatile holographic system, the amplitude of the refractiveindex changes is greatly increased and the recording sensitivity is largely enhanced by recording with UV light in the （Ce, Cu） ： LiNbO3 crystals. Temporal evolutions of the photorefractive grating and the diffraction efficiency are effectively described and numerically analyzed based on jointly solving the two-center material equations and the coupled-wave equations. Roles of doping levels and recording-beam intensity in the process are discussed in detail. Investigations show that gratings recorded in the deep and shallow centers are in phase, the value of the total grating （the superimposition of the deep and shallow gratings） is the summation of those of the two gratings; in the fixing phase, the depth of grating in the deep center is enhanced; the amplitude of the refractive-index changes increases with increasing the concentrations of the deep and shallow centers, and larger recording intensity results in the stronger total grating and the larger value of the recording sensitivity. Theoretical results can confirm and predict experimental results.