Application of Liquid Crystals for tunable Photonic Crystals

该项目致力于研究空间周期性纳米结构，其中一个成分是液晶。众所周知，液晶是双折射的，其折射率强烈地依赖于温度。此外，还可以通过施加电场和磁场来重新定位光轴。由于光子带隙强烈地依赖于相应介质的折射率，因此原则上可以通过改变温度或外部磁场或电场来改变包含液晶的光子晶体的光学性质。在拟议的项目中，应研究这种影响的实际可能性和限度。我们计划研究三种不同类型的模型系统：首先，我们计划将液晶渗透到胶体晶体(人造蛋白石)和反胶体晶体中，并研究外场对这些结构的影响。作为第二种类型的系统，我们希望研究填充了液晶的硅或氧化铝中的微加工结构。研究方法包括光谱和电光表征、会聚光衍射实验和近场扫描光学显微镜(NSOM)。第三类系统由液晶组成，具有晶格状的超结构。这些材料将用于研究空间周期性环境对有机染料分子发射的影响。

The project which is proposed here, is devoted to the investigation of spatially periodic nanostructures where one of the components is a liquid crystal. It is well known that liquid crystals are birefrigent, and that their refractive indices depend strongly on temperature. Moreover, the optical axis can be reoriented by applying electric and magnetic fields. Since the photonic bandgap depends strongly on the refractive indices of the corresponding media, it is in principle possible to vary the optical properties of a photonic crystal containing a liquid crystal by changing the temperature or the external magnetic or electric field. The practical possibilities and limits of this effect shall be studied in the proposed project. We plan to study three different types of model systems: In the first place, we plan to infiltrate a liquid crystal in colloidal crystals ("artificial opals") and inverse colloidal crystals and to study the effect of external fields on these structures. As a second type of system, we wish to study microfabricated structures in silicon or aluminium oxide which are filled with a liquid crystal. The methods of investigation include the spectroscopic and electrooptic characterization, diffraction experiments with convergent light, and near-field scanning optical microscopy (NSOM). The third type of systems consists of liquid crystals exhibiting a lattice-like superstructure. These materials will be used in order to study the influence of a spatially periodic environment on the emission of organic dye molecules.