【摘要】 利用Kirchhoff-Fraunhofer衍射积分原理研究了实验中观察到的C₆₀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C₁和C₂。当C₁和C₂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C₁和C₂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。更多还原

【Abstract】 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 C₁ 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.更多还原