Nanophotonic nonlinear and laser devices exploiting bound states in the continuum

Abstract

Bound states in the continuum, for decades a theoretical curiosity, have more recently found application in nanophotonic platforms due to their high quality factors and spatial confinement. Here, the authors review recent progress in the development of active and passive photonic devices exploiting these properties. The quality factor (Q), describing the rate of energy loss from a resonator, is a defining performance metric for nanophotonic devices. Suppressing cavity radiative losses enables strong nonlinear optical responses or low-power operation to be achieved. Exploiting long-lived, spatially-confined bound states in the continuum (BICs) has emerged from the numerous approaches considered as a promising route to boost nanophotonic Q factors. Initial research explored the formation mechanisms of various types of BICs, drawing parallels to topological physics. With these fundamentals now established, we review the recent application of BICs in passive and active nanophotonic devices.