CHAPTER 5: Optical Properties of Tunable Photonic Crystals Using Liquid Crystals

Liquid crystals are mesophases between crystalline solids and isotropic liquids. Their fluidity and dielectric anisotropy allow molecular reorientation in nanostructures. Since the field‐induced molecular reorientation gives rise to a change in optical properties, liquid‐crystal infiltrated photonic crystals have been regarded as potential candidates for tunable photonic crystals. In this chapter, the fundamentals of photonic crystals are described to explain photonic band structures, photonic bandgaps, and defect modes. A one‐dimensional photonic crystal with a liquid‐crystal defect layer is experimentally studied for application as a tunable laser, an electro‐optics switch, and a controllable polarizer. Numerical analyses are also carried out to simulate the physical properties: photonic band structures, light propagation, electric‐field enhancement, density of states, and dynamic response of liquid crystals. Further, tunable negative refraction is also numerically examined using a 2D triangular lattice photonic crystal infiltrated with a liquid crystal.