Three-dimensional nano-periodic liquid crystals and their application to photonic crystal device

研究了具有自组织纳米周期结构的胆甾相和手性近晶液晶的三维纳米周期结构。在染料掺杂胆甾相液晶的焦点圆锥结构中观察到了电调谐激光。这种激光作用是基于焦点圆锥域中的螺旋微腔。在一维周期结构中，利用NLC和共轭聚合物的堆积层作为缺陷层，实现了缺陷模激光波长的电调谐。由于电场诱导NLC分子重新排列引起缺陷层折射率的变化，导致了激光波长随外加电场的变化而广泛调谐。在由两层光聚合胆甾相液晶(PCLC)组成的复合膜的透射谱中，实验证明了扭转缺陷模(TDM)和基于TDM的激光，其中PCLC的自组织螺旋结构起到一维光子晶体的作用，而在两层PCLC层的界面处，指向矢围绕螺旋轴旋转的不连续性导致了TDM。提出了在染料掺杂向列相液晶(NLC)光波导中利用全息激发实现光泵分布反馈激光的方法，即在外加电场的情况下实现激光波长的连续调谐。

Three-dimensional nano-periodic structures based on cholesteric and chiral smectic liquid crystals having a self-organized nano-periodic structure have been investigated. The electrically tunable lasing has been observed in a focal conic structure of dye-doped cholesteric liquid crystal. This laser action is based on a helix micro-cavity in focal conic domains. Electrical tuning of the wavelength of the defect mode lasing in a one-dimensional periodic structure has been demonstrated using a stacked layer of NLC and conjugated polymer as a defect layer in the periodic structure. Lasing wavelength is widely tuned upon applying the electric field, which is due to the refractive index change in the defect layer caused by the field-induced realignment of the NLC molecules. Twist defect mode (TDM) and a lasing based on TDM have been experimentally demonstrated in a transmission spectrum of the composite film consisting of two photopolymerized cholesteric liquid crystal (PCLC) layers in which self-organized helical structure of PCLC acts as one-dimensional photonic crystal and a discontinuity of the director rotation around the helix axis at an interface of two PCLC layers induces the TDM. Optically pumped distributed feedback lasing has been proposed in a dye-doped nematic liquid crystal (NLC) waveguide by holographic excitation, in which continuous tuning of the lasing wavelength is performed upon applying electric field.