Ultrafast all-optical tunable Fano resonance in nonlinear metamaterials

An ultrafast all-optical tunable Fano resonance is realized in a nonlinear metamaterial composed of arrays of asymmetrically split rings etched in a gold film, coated with a polycrystalline lithium niobate layer. The metamaterial has a large optical nonlinearity because of strong nonlinearity enhancement associated with field reinforcement provided by plasmonic resonance, and quantum confinement effect provided by nanoscale crystal grains. A large shift of 23 nm in the Fano resonance wavelength is achieved under excitation of a weak pump light with an intensity of 15 MW/cm2. While an ultrafast response time of 48 ps is also maintained.