A review for optical sensors based on photonic crystal cavities

This review covers photonic crystal cavities (PCCs) and their applications in optical sensors, with a particular focus on the structures of different PCCs. For each kind of optical sensor, the specific measurement principle, structure of PCC, and the corresponding sensing properties are all presented in detail. The summary of the reported works and the corresponding results demonstrate that it is possible to realize miniature and high-sensitive optical sensors due to the ultra-compact size, excellent resonant properties, and flexibility in structural design of PCCs. Finally, the key problems and new directions of PCCs for sensing applications are discussed.