白光在LiNbO_3∶Fe晶体中写入的任意折射率分布光波导

Fabrication of Waveguides with Arbitrary Index Profiles in LiNbO_3∶Fe Crystal by White Light Irradiation

在理论分析Li NbO3∶Fe晶体中光致折射率变化分布与写入光的强度分布之间关系的基础上,提出了一种在该晶体中写入具有任意折射率分布光波导的新方法.利用由白光经电寻址空间光调制器得到的强度分布不同的片光辐照晶体,分别写入了折射率呈误差函数分布和平方律分布的光波导结构.采用干涉法测量了晶体中的光致折射率变化,并用推导出的折射率变化分布解析表达式很好地拟合了测量数据.实验结果表明,该方法是可行的.利用白光光源结合高分辨率的空间光调制器有望在多种光折变材料中制备出具有任意折射率分布的高质量光波导.

On the basis of the theoretical analysis of the relations between the distributions of light-induced index changes and the intensity profiles of writing beams, a novel optical approach for fabricating waveguides with arbitrary index profiles is proposed. Waveguide structures with index profiles of an error function distribution and a square law distribution are fabricated respectively employing writing beams with different intensity profiles generated by a white light beam reading out gray patterns from an electrically addressed spatial light modulator （SLM）. Employing the interferometric technique,the light-induced index changes in the crystal sample are measured, which are well fitted by using the deduced analytic expressions of the index change distributions. Experimental results show that the method is feasible. High quality waveguide devices with arbitrary index profiles may be fabricated in various photorefractive media employing white light irradiations and spatial light modulators with high resolutions.