Manipulating Light with Bound States in the Continuum: from Passive to Active Systems

Abstract The manipulation of light has become the focus of various modern optical technologies. The emergence of bound states in the continuum (BICs) offers an alternative platform for controlling light, including the confinement and manipulation of polarization, amplitude, and phase. Currently, research on photonic BICs is maturing, with extensive exploration of methods for achieving BICs and their various applications, including lasing, sensing, and enhanced light‐matter interaction. In this review, an overview of photonic BICs is provided. Specifically, the unique properties of BICs are first presented, followed by their state‐of‐the‐art applications in passive systems, ranging from sensing to waveguiding, beam shaping, and chirality. The paradigm‐shifting developments in active systems resulting from the hybridization of BICs with active and novel materials are then highlighted. Finally, some of the challenges facing photonic BICs are discussed, along with future directions in terms of physics, design, fabrication, engineering, and tunability.