C_(60)掺杂向列相液晶薄膜的激光诱导自衍射现象研究  

Investigation of Self-Diffraction Effect in C_(60)-Doped Nematic Liquid Crystals Induced by Gaussian Beam

作　　者：任常愚[1,2] 孙秀冬[1] 刘正君[3] 裴延波[1] 

机构地区：[1]哈尔滨工业大学物理系,黑龙江哈尔滨150001 [2]黑龙江科技学院数力系,黑龙江哈尔滨150027 [3]哈尔滨工业大学自动化测试与控制系,黑龙江哈尔滨150001

出　　处：《光学学报》2009年第3期772-777,共6页Acta Optica Sinica

基　　金：国家自然科学基金(90201003);黑龙江省教育厅科学技术研究项目(11531330)资助课题。

摘　　要：利用Kirchhoff-Fraunhofer衍射积分原理研究了实验中观察到的C_(60)掺杂垂直排列向列相液晶(5CB)液晶薄膜的远场衍射图样。模拟计算结果表明:实验中观察到的衍射圆环是不同实验参数的结果,并给出了确定衍射圆环结构的主要参数C_1和C_2。当C_1和C_2的符号相同时,远场会出现中心强度最大,向外逐渐减弱,分布尺度较小的细衍射环;当C_1和C_2的符号相反时,远场会出现中央较暗,向外逐渐增强,分布尺度较大的粗衍射环。衍射圆环的产生可由高斯光束通过非线性样品是引起附加相位的自相位调制现象来解释。将使液晶材料应用于光限幅等光子学领域。Based on the Kirchhoff-Fraunhofer diffraction integral, a theoretical study, with reference to experimental results, of transverse self-phase modulation effects in the transmission of a laser beam through a homeotropic C60-doped nematic liquid crystal （5CB） cell was presented. Two different type of concentric diffraction rings were observed in the far field. The simulation results show that, the diffraction rings were determined by the two factors of C2 and C2. When the sign of C1 is identical to that of the C2, the pattern in the far field is a series of thin, narrow diffraction rings with a central bright spot. When the sign of C1 is opposite to that of the C2, the thick diffraction ring pattern with central dark spot and the large distribution range will emerge in the far-field plane. The phenomenon is attributed to the spatial self-phase modulation caused by the refractive index change of the medium when the Gaussian beam passes through the sample. The results show that the theoretical analysis is consistent with the observed experimental phenomena, which is significant in the applications of practical nonlinear optical limiters for the eye or sensor protection.

关 键 词：非线性光学 自衍射 向列相液晶 白相位调制 高斯光束 

分 类 号：O753.2[理学—晶体学]