**Abstract**

In this chapter, the current research and development of the liquid crystal-based photonic crystals is introduced. This chapter will present the essential knowledge of the new photonic crystal technology and applications in simple language. In the recent year, liquid crystal-enabled photonic crystal technologies have attracted broad attentions from scientists. Based on special optical properties of liquid crystal-enabled photonic crystal device, many applications, such as tunable optical filters, tunable optical modulators, optical pulse compressors, laser device, and applications in multiphoton microscopy, have been developed in recent years. In addition, the detailed optical properties, operation principles, and prospects are discussed in this chapter.

**Keywords:** photonic crystals, liquid crystals, photonic band gap, electro-optic device, optical properties
