Recent Progress in Photonic Crystal Devices and Their Applications: A Review

The research field of photonic crystals (PhCs) remains active on a global scale. PhCs, which are periodic optical nanostructures with the characteristics of excellent light field confinement and numerous varying degrees of freedom, provide a solid foundation for controlling the movement of light. Periodic variation of the index of refraction in two or three spatial dimensions with a substantial high-to-low ratio generates a number of intriguing phenomena and enables a variety of potential functionalities. Recently, intriguing devices based on PhCs, such as Y-branches, small-diameter bent waveguides, and miniature resonator cavities, have been proposed and extensively utilized. PhC waveguides are considered ideal candidates for a variety of applications, such as in power splitters, logic gates, sensing and communication fields, etc. These exceptional characteristics may facilitate the development of a dense integrated circuit. However, PhC technology is still relatively new and therefore requires additional effort to fully exploit it. This paper reviews the most popular and essential optical components based on PhCs, including power splitters, modulators, polarization maintaining devices, sensors, and lasers, to summarize the most recent developments relating this hot topic. These devices have superior performance and a smaller footprint compared to conventional photonic devices.