Non-linear Metasurfaces Based on Epsilon-Near-Zero Thin Films

Nonlinear effects hold great potential for a wide range of applications - all-optical signal processing, beam shaping and steering, optical computing, sensing, detection and general meteorology, to name a few. However, typically non-linear effects are weak; a typical non-linear index change is on the order of 0.01% or less and therefore they typically require high-power, short-pulse lasers, as well as long interaction length or resonant enhancement. Here, we show that a thin metasurface (50 nm total thickness), consisting of metal antennas on an epsilon-near-zero (ENZ) film, can produce a giant non-linear response with the refractive index change, Δn, exceeding 2 across a broad spectral range in the near-infrared, including the commercially important C and L band regions.