  Recent advancements in photonic bound states in the continuum (BICs) have
opened up exciting new possibilities for the design of optoelectronic devices
with improved performance. In this perspective article, we provide an overview
of recent progress in photonic BICs based on metamaterials and photonic
crystals, focusing on both the underlying physics and their practical
applications. The first part of this article introduces two different
interpretations of BICs, based on far-field interference of multipoles and
near-field analysis of topological charges. We then discuss recent research on
manipulating the far-field radiation properties of BICs through the engineering
of topological charges. The second part of the article summarizes recent
developments in the applications of BICs, including chiral light and vortex
beam generation, nonlinear optical frequency conversion, sensors, and
nanolasers. Finally, we conclude with a discussion of the potential of photonic
BICs to advance terahertz applications in areas such as generation and
detection, modulation, sensing, and isolation. We believe that continued
research in this area will lead to exciting new advancements in
optoelectronics, particularly in the field of terahertz devices.
