平行排列丝状液晶在超短脉冲激光激励下发生瞬态扭曲形变的最佳偏振角

The initial angle solution for the ultra-short laser pulse induced transient twist reorientation in a plane-aligned nematic liquid crystal

利用光学相位延迟法 ,观察到平行排列丝状液晶在超短脉冲激光 (10ns)激励下的瞬态扭曲形变 .实验结果表明 ,虽然脉冲激光的电场强度远远大于液晶发生扭曲形变的阈值 ,但并不能保证液晶会发生瞬态扭曲形变 .这主要是因为脉冲激光的激励时间非常短 ,而液晶分子发生扭曲形变的响应时间相对较长 ,从而使其来不及形变 .分析发现 :激励激光的偏振方向与平行排列丝状液晶分子的最佳夹角是 4 5°.利用此条件 ,观察到掺微量D型苏氨酸卟啉的平行排列丝状液晶在超短脉冲激光激励后具有记忆效应 ,这在光存储和记忆显示方面有很大的实用价值 .

The optical phase retardation method was employed to observe the transient twist reorientation effect of a plane-aligned nematic liquid crystal induced by ultra-short laser pulses. The experimental result indicated that, although the electric field intensity of laser pulses is much higher than that needed for twist deformation, it does not ensure the twist reorientation under the laser pulse. This is because the width of laser pulse is very short and the response time for the twist reorientation is very long. To overcome this barrier an optimum angle (45degrees) between the polarization of the laser pulse and the director orientation in substrates is found by analysis. Using this initial angle, we observed a plane-aligned nematic liquid crystal cell doped with a few o-(D-Thr) N-C-2-(TPP) to possess memory effect after the laser pulse pump, which was important in optical data storage and memory display.