Ultralow-power all-optical tunable dual Fano resonances in nonlinear metamaterials

Dual Fano resonances are realized in a nonlinear photonic metamaterial consisting of periodic arrays of asymmetrical meta-molecules etched in a gold film coated with azobenzene polymer layer made of poly[(methyl methacrylate)-co-(disperse red 13 acrylate)]. Enormously enhanced photoisomerization associated with resonant excitation brings about a large refractive index variation in the azobenzene polymer. Under excitation of a weak pump light as low as 0.61 kW/cm2, a large shift of 50 nm in the Fano resonance wavelength is obtained. Compared with previous reports, the threshold pump intensity is reduced by seven orders of magnitude while a large tunability is maintained simultaneously