Studies of photonic crystal structures infiltrated with liquid crystals

摘要

This paper investigates the tunable characteristics of various photonic crystal structures infiltrated with nematic liquid crystals. A triangular lattice of air cylinders drilled into silicon provides the photonic crystal structure and the nematic material is inserted either in all or in properly selected air voids in order to create one-dimensional cavities or directional couplers. We have shown in previous studies that the spectral properties of such geometries can be tuned by means of applying appropriate static electric fields, which eventually determine the orientation of the liquid crystal molecules inside the cylindrical cavities. The essential aspect of the present study is to consider various profiles for the nematic director, which are associated with different molecular anchoring conditions at the confining surfaces, as well as electric fields of various strengths and orientation. In particular, we examine the cases of homeotropic or tangential surface anchoring orientation in the strong or weak anchoring limit, and more specifically focus on determining the impact of the transition from strong to weak anchoring, both on the operation of each structure and the associated range of tuning.