摘要:
采用激光染料DCM、向列相液晶TEB30A、手性剂S-811、聚乙烯醇(PVA),通过微胶囊法制备了聚合物分散胆甾相液晶薄膜,测量激光辐射谱,研究了其激光辐射机理和温度调谐特性.利用正交偏光显微镜观察器件织构,看到液晶微滴分散均匀,尺寸较大,约为80μm,并且微滴中液晶分子呈现平面态排列织构.以532 nm的Nd：YAG固体激光器作为抽运源,测得在634.5 nm和680.2 nm波长处出现了尖锐的激光辐射峰,线宽分别约为0.25 nm,0.29 nm.并与染料掺杂胆甾相液晶激光器件进行比较.升高器件温度,其输出激光波长蓝移,获得666.7 nm至643.9 nm共22.8 nm的调谐范围.由实验结果分析得出,激光辐射机理为光子禁带末端激光,出射波长分别对应光子禁带的两个边沿.
Abstract:
In this work, laser dye DCM, nematic liquid crystal TEB30A, chiral dopant S-811 and PVA are used to pre-pare polymer dispersed cholesteric liquid crystal (LC) films by the method of microcapsule. Lasing mechanism and temperature-tunable characteristics of the films are investigated. The diameters of large droplets in the films are about 80 μm and LC molecules are planar-textured in the droplets when viewed between crossed polarisers through a polar-ization microscope. Pumped by the 532 nm Nd:YAG laser, narrow linewidths in laser emissions are obtained at 634.5 nm and 680.2 nm, and the linewidths are of 0.25 nm and 0.29 nm, respectively. The device is then compared with a dye-doped cholesteric liquid crystal laser. The wavelength of output laser will blueshift when the temperature of the device is increased, and a 22.8 nm tunable lasing, from 666.7 nm to 643.9 nm, is obtained. Analysis concludes that the lasing mechanism of the film is band-edge lasing, and the emission wavelengths are corresponding to the two edges of the photonic band gap.
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