Resonant dielectric metasurfaces in strong optical fields

Optical materials are undergoing revolutionary transformations driven by nanotechnology. Our ability to engineer structures at a scale smaller than the wavelength of light enables new properties and functionalities otherwise not available in natural bulk optical materials. A class of such components—dielectric metasurfaces—employs two-dimensional arrays of designer resonant nanoscale elements whose optical response is defined by their geometry. While linear regimes of interactions between dielectric metasurfaces and moderately intense light have already formed a mature field of applied research and engineering, new frontiers are being actively explored in the nonlinear optical regime describing interactions of metasurfaces with strong optical fields. In this Research Update, we cover the most recent progress along with several directions of research within the field of nonlinear optics of dielectric metasurfaces. Specifically, we review approaches to design and fabricate metasurfaces with high local field enhancements that facilitate nonlinear light–matter interactions, outline nonlinearity-enabled functionalities of dielectric metasurfaces, explore resonant metasurfaces in the strong-field non-perturbative regime, and discuss the implications of the time-variant refractive index in metasurfaces that interact with strong optical fields produced by laser pulses.