弱磁场下研究掺杂微量Pr_2O_3的向列相液晶TEB30A薄膜的衍射
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摘要
采用1.5 m W低功率的He-Ne激光(632.8 nm)正入射掺杂微量Pr_2O_3的向列相液晶TEB30A(TEB30A/Pr_2O_3)薄膜,研究在不同强度的弱磁场(0、0.4649 T、0.5062 T和0.5185 T)中的远场衍射特性。实验结果表明,在相同的条件下,当弱磁场强度超过一定的阈值时,在向列相液晶TEB30A中掺杂微量Pr_2O_3会非常明显地改善衍射图样的效果。基于Kirchhoff-Fraunhofe衍射积分原理的理论模拟结果表明,当磁场强度超过一定的阈值,微量Pr_2O_3掺杂之所以能明显地改善样品的衍射,是由于Pr_2O_3的掺杂增大了向列相液晶薄膜样品的非线性相移。TEB30A/Pr_2O_3薄膜的远场衍射消除了激光散度的影响。这一掺杂技术可应用于磁控光开关及光限幅等领域。
The far-field diffraction characteristics of TEB30 A/Pr_2O_3 film was studied in the different weak magnetic field(0 T,0. 4649 T,0. 5062 T and 0. 5185 T) with the low power He-Ne laser of 1. 5 m W(632. 8 nm) at normal incidence. The experiment results showed that in the same conditions,when the weak magnetic strength exceeded a certain threshold,the diffraction effects of sample doped with trace Pr_2O_3 could obviously be improved.The diffraction pattern could become clear with the magnetic strength increasing. Based on the Kirchhoff-Fraunhofer diffraction integral,the theoretical simulation results showed that micro Pr_2O_3 doping could obviously improve the diffraction of sample when the weak magnetic strength exceeded a certain threshold because the doping of Pr_2O_3 increased the nonlinear phase shift of the nematic liquid crystal sample. The far-field diffraction of the TEB30 A/Pr_2O_3 film could eliminate the effects of the divergence of the laser beam. Therefore the technology can be applied to the areas of magnetic optical switch and optical limiters.
The far-field diffraction characteristics of TEB30 A/Pr_2O_3 film was studied in the different weak magnetic field(0 T,0. 4649 T,0. 5062 T and 0. 5185 T) with the low power He-Ne laser of 1. 5 m W(632. 8 nm) at normal incidence. The experiment results showed that in the same conditions,when the weak magnetic strength exceeded a certain threshold,the diffraction effects of sample doped with trace Pr_2O_3 could obviously be improved.The diffraction pattern could become clear with the magnetic strength increasing. Based on the Kirchhoff-Fraunhofer diffraction integral,the theoretical simulation results showed that micro Pr_2O_3 doping could obviously improve the diffraction of sample when the weak magnetic strength exceeded a certain threshold because the doping of Pr_2O_3 increased the nonlinear phase shift of the nematic liquid crystal sample. The far-field diffraction of the TEB30 A/Pr_2O_3 film could eliminate the effects of the divergence of the laser beam. Therefore the technology can be applied to the areas of magnetic optical switch and optical limiters.
引文
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[3]Babak Olyaeefar,Habib Khoshsima.Faster electro optical switching with a highly viscous nematic liquid crystal mixture[J].Opt Quant Electron,2014,46(2):357-363.
[4]Chernyshuk S B.High-order elastic terms boojums and general paradigm of the elastic interaction between colloidal particles in the nematic liquid crystals[J].European Physical Journal E,2014,37(6):1-9.
[5]Michael J,Mac Neil L,Smyth N F,et al.Exact and approximate solutions for optical solitary waves in nematic liquid crystals[J].Physica D,2014,284(12):1-15.
[6]Iam Choon Khoo.Nonlinear optics,active plasmonics and metamaterials with liquid crystals[J].Quantum Electronics,2014,38(2):77-117.
[7]Nader Noroozi·Dana Grecov.Numerical simulation of three-dimensional flow-induced microstructure in a simplified prosthetic hip joint with nematic liquid crystal lubricant[J].Rheol Acta,2014,53(5-6):457-465.
[8]Zolot’ko A S,Kitaeva V F,Kroo N,et al.The effect of an optical field on the nematic phase of the liquid crystal[J].Ocbp Jetp Lett,1980,32(2):158-162.
[9]Durbin S D,Arakelian S F,Shen Y R.Laser-induced diffraction rings from a nematic liquid-crystal film[J].Opt Lett,1981,6(9):411-413.
[10]Santamato E,Shen Y R.Field-curvstare effect on diffraction ring pattern of a laser beam dressed by spatial self-phase modulation in a nematic film[J].Opt Lett,1984,9(12):564-566.
[11]Bloisi F,Vicari L,Simoni F,et al.Self-phase modulation in nematic liquid crystal films detailed measurements and theoretical calculations[J].J Opt Soc Am B,1988,5(12):2462-2466.
[12]Khoo I C,Finn G M,Michael R R,et al.Passive optical self-limiter using laser-induced axially asymmetric and symmetric transverse self-phase modulations in nematic liquid crystals[J].Opt Lett,1986,11(4):227-229.
[13]任常愚,孙秀冬,刘正君,等.C60掺杂向列相液晶薄膜的激光诱导自衍射现象研究[J].光学学报,2009,29(3):772-777.Ren C Y,Sun X D,Liu Z J,et al..Investigation of self-diffraction effect in C60-doped nematic liquid crystals induced by Gaussian beam[J].Acta Optica Sinica,2009,29(3):772-777.
[14]Brochard F,Gennes P G D.Theory of magnetic suspensions in liquid crystals[J].Journal of Physique,1970,31(7):691-708.
[15]Zhou S,Nastishin Y A,Omelchenko M M,et al.Elasticity of lyotropic chromonic liquid crystals probed by director reorientation in a magnetic field[J].Physical Review Letters,2012,109(3):037801(1-15).