梳状电极胆甾相液晶激光器的激光辐射谱

Lasing Spectrum of Cholesteric Liquid Crystal with Interdigitated Electrodes Pattern

设计制作了梳状电极染料掺杂胆甾相液晶激光器件,研究了外加电压下的激光辐射谱。器件的下基板ITO电极刻蚀成梳状条形电极,电极宽度约2 mm,相邻电极间距分别约为1,3,5 mm。上基板无ITO电极。上下基板取向膜平行摩擦取向处理,使胆甾相液晶平面态排列。以532 nm的Nd:YAG激光器作为泵浦光源,测量器件激光辐射谱。改变外加电压0~100 V,3个区域均出现了多模输出。在1 mm电极间距区域,可获得633.65~621.52 nm(12 nm)和683.15~664.35 nm(18 nm)的可调谐波长范围;在电极间距3,5 mm区域,辐射激光波长变化微小。在外加电压作用下,液晶分子均匀的螺旋周期排列受到扰动,液晶分子层螺旋轴倾斜,各个液晶畴的螺旋轴取向不一致,使有效螺距值缩短并有所浮动,引起出射激光波长蓝移和多模输出。利用光子态密度理论数值模拟了激光辐射谱。当有效螺距为倾斜角的函数时,随着倾斜角增大出射激光波长蓝移。

The dye doped cholesteric liquid crystal(CLC)laser with interdigitated electrodes pattern was designed and the lasing spectra of the device in different voltages were investigated.The bottom glass substrate was patterned with interdigitated ITO electrode using the laser etching method.The width of a single electrode was approximately 2 mm and the distances between neighboring electrodes were approximately 1,3 and 5 mm,respectively.There were no ITO electrodes on the upper glass substrate.In order to achieve a planar alignment state of CLC,a parallel rubbing treatment was performed on both substrates.A 532 nm Nd∶YAG pulsed solid-state laser was used to pump the cell.When the voltage changed from 0 to 100 V,a multi-wavelength lasing was obtained.A tunable output lasing was obtained at the wavelength range of 633.65-621.52 nm(12 nm)and 683.15-664.35 nm(18 nm)where the distance between neighboring electrodes was approximately 1 mm.However,the lasing spectra were scarcely modified if the distances between neighboring electrodes were approximately 3 mm and 5 mm.Under an applied external voltage,the uniform helical alignment of CLC was disturbed and the helical axis was tilted.This cause equivalent helical pitch shrinks and floating.Therefore,the output lasing wavelength can be blue-shifted and multimode lasing was presented.The lasing spectrum was simulated using optical density theory.When the helical pitch is a function of a tilt angle,the output lasing blue-shift increases with tilt angle.