Large optical nonlinearity of dielectric metasurface-assisted Mie resonance strongly coupled to an epsilon-near-zero mode

Abstract

Light-matter strong coupling provides a powerful way to modify the nonlinear optical properties of materials. The coupling strength of the state-of-the-art strongly coupled systems are restricted by weak field confinement of the cavity, which limits the enhancement of the optical nonlinearity. Here, we investigate a new type of strong-coupling system, where the Mie resonant modes of the dielectric nanocavities are strongly coupled to an epsilon-near-zero mode, which results in an Rabi splitting of 220 meV. Static and dynamic nonlinear optical measurements reveal a very large enhancement in the intensity-dependent refractive index change at the coupled resonance. In addition, we observe a transient response of hundreds of femtoseconds for the coupled system. The ultrafast and large optical nonlinear coefficients in this work offer a new route towards strong coupling-assisted high-speed photonics.