电场作用下染料掺杂手性向列相液晶器件激光辐射谱研究

A Study of Lasing Spectrum of Dye-Doped Chiral Nematic Liquid Crystal Cell under Electric Field

研究了电场作用下染料掺杂手性向列相液晶器件激光辐射谱。设计了两种电极结构,分别对正性和负性液晶器件施加横向和纵向电场,采用532nm的Nd∶YAG脉冲固体激光器泵浦样品。对正性液晶器件施加电场,在630~660nm范围获得多波长的激光输出。对负性液晶激光器件施加电场,获得调谐范围为18.5nm的激光输出。由器件织构和光子禁带的变化,进行了深入的分析。正性液晶器件,在电场力矩与扭曲力矩相互竞争过程中,引起液晶的流动,光子禁带上下浮动,因此不仅在禁带边沿,禁带内也出现激光辐射。而负性液晶器件随着电场强度增大,液晶螺距收缩,禁带蓝移,输出激光波长从681.0nm蓝移到662.5nm,出射激光波长为光子禁带边沿处。负性液晶器件在电场作用下的稳定性较好。

The lasing spectrum of dye-doped chiral nematic liquid crystal under electric filed was investigated.Two kinds of electrodes were designed to apply transverse electric field to positive liquid crystal cell and longitudinal electric field to negative liquid crystal cell.A 532 nm Nd∶YAG pulsed solid-state laser was used to pump the cell.When transverse electric field is applied to positive liquid crystal device,multi-wavelength laser output is obtained in the range of 630~660nm.When longitudinal electric field is applied to negative liquid crystal cell,18.5nm tunable output lasing is obtained.The output characteristic of cell was analyzed from the texture of device and the photonic band gap.In the positive liquid crystal cell,the competition of electric moment with twisting moment causes the flow of LC molecule,and the flow of LC molecule leads to a floating photonic band gap.For this reason,not only at the edge of photonic band gap but in the photonic band gap can produce lasing.For negative liquid crystal cell,the pitch shrinks with the increase of electric field.The photonic band gap shows blue-shift with the decrease of pitch.and Lasing wavelength is blue shifted from 681.0 to 662.5nm and the lasing at the edge of photonic band gap.Negative liquid crystal cell has better stability under electric field effect.