掺杂Sm_2O_3的向列相液晶TEB30A光栅衍射特性研究

基于光学琼斯矩阵理论,研究掺杂Sm_2O_3的向列相液晶TEB30A在弱磁场中的光栅衍射特性。结果表明,自然光通过处在弱磁场中的适量配比的Sm_2O_3/TEB30A样品后,会在远场产生衍射条纹,且衍射条纹会随外磁场强度的增加而出现动态的变化。产生衍射条纹是由于适量的Sm_2O_3的掺杂,使得向列相液晶TEB30A的折射率各向异性Δn沿外磁场方向呈现周期分布,形成了液晶光栅;当外磁场强度发生变化时,处在外磁场中的Sm_2O_3粒子和液晶分子的分布会随之发生变化,导致Δn沿外磁场分布的周期发生变化,从而引起液晶光栅常数发生变化,因此,衍射条纹呈现出动态变化的效应。模拟结果表明,当外磁场强度由0.464 9T增加到0.518 5T时,液晶光栅常数由0.5cm降到0.4cm。这一技术研究方法将大大降低液晶光栅的成本,同时,弱磁场环境也为使用者提供了一种安全的使用环境。

Diffraction characteristics of nematic liquid crystal TEB 30 A grating doped with Sm2O3

Based on the theory of the optical Jones matrix,the grating diffraction of the nematic liquid crystal TEB30A doped with Sm₂O₃ is studied in the weak magnetic field. The results show that when the natural light passes through the sample of the proper proportion of Sm₂O₃/TEB30A in the weak magnetic field, the diffraction stripes appear in the far field. And the diffraction stripes will change dynamically with the increase of the intensity of the external magnetic field. The reason for producing the diffraction stripes is that the proper Sm₂O₃ particles make the refractive index anisotropy Δn of the nematic liquid crystal TEB30A exhibit the periodic distribution along the direction of the external magnetic field, which leads to the formation of the grating in the liquid crystal. When the external magnetic field varies in the intensity, the distribution of Sm₂O₃ particles and liquid crystal molecules in the external magnetic field will change accordingly, which causes the period of the distribution of Δn along the external magnetic field to change. As a result, the constant of the liquid crystal grating changes. Therefore, the diffraction stripes exhibit a dynamic effect. The simulation results show that the grating constant of the Sm₂O₃-doped nematic liquid crystal TEB30A decreases from 0.5 cm to 0.4 cm with the magnetic strength increasing from 0.464 9 T to 0.518 5 T. The technical method will greatly reduce the costs of the liquid crystal grating, and make operator work in a safe setting.