光强变化对双中心非挥发光折变局域体光栅的影响

Influence of Light Intensity Change on Two-Central Nonvolatile Crossed-Beam Photorefractive Gratings

为研究局域体光栅的光折变形成机制及衍射特性,以双中心非挥发全息记录方案为基础,将带输运模型与二维耦合波理论相结合,采用数值模拟的方法,研究紫外敏化光强和记录红光总光强的变化对LiNbO_3:Fe:Mn晶体中局域体光栅的影响,并给出定影结束时平均折射率调制、衍射光波振幅及衍射效率的模拟结果。研究发现:记录红光总光强不变时,平均折射率调制随紫外敏化光强增加而增加,而紫外敏化光强的改变对衍射波振幅的分布影响不大,衍射效率随紫外敏化光强度的增大先增大后减小,存在最佳紫外敏化光强,以获得80%以上的最高衍射效率。当紫外敏化光强不变时,随着记录红光总光强的增加,记录折射率光栅逐渐减弱,衍射波振幅分布变得越来越均匀,衍射效率逐渐降低。

Based on the two-center nonvolatile holographic recording method and the theory model combining band transport model with the two-dimensional coupled-wave equations, the numerical simulation method is used to study the photorefractive formation and diffractive properties of the crossed-beam photorefractive gratings. The influence of the intensity change of sensitizing ultraviolet （UV） light and the total intensity change of the recording red light on nonvolatile crossed-beam photorefractive gratings in LiNbO3.. Fe： Mn crystals is investigated. And the results, including the average refractive index modulation, the spatial distribution of the diffracted intensity and the diffracted efficiency at the fixing end, are obtained. When the UV light intensity increases under fixed red light intensity, the average refractive index modulation increases accordingly, the spatial distribution of the diffracted intensity is almost unchanged and the diffraction efficiency increases firstly and then decreases. There is an optimal intensity for the sensitizing UV light to achieve the maximum diffraction efficiency （higher than 80 % ）. When the intensity of the sensitizing UV light is fixed, with increasing recording red light intensity, the index grating recorded wears off, the spatial distribution of the diffracted intensity is more and more homogeneous, and the diffraction efficiency decreases.