Metadevices empowered by bound states in the continuum

We review the physics of photonic bound states in the continuum (BICs) and their applications to metadevices, including enhancement of nonlinear response, light-matter interaction, and development of active nanophotonic devices. In particular, we discuss how BIC-empowered dielectric metastructures can be used to generate efficiently high-order optical harmonics from bulk and to boost the intrinsic nonlinearity of transition metal dichalcogenide (TMD) flakes. We explore TMD resonators composed of structured dielectric arrays and individual nanoparticles for strong light-matter coupling phenomena. We discuss the extension of metasurface functionalities for biosensing applications in biomarker detection and quantum information processing with entangled photons. Finally, we demonstrate how tunability of BICs in the momentum space can be used to realize a novel type of efficient lasing based on a finite-size cavity with a small footprint.