Double-resonance plasmon-driven enhancement of nonlinear optical response in a metamaterial with coated nanoparticles

By means of a simple analytical model, we show the possibility of giant double-resonance enhancement of nonlinear cubic optical response of metamaterial containing layered (coated) nanoparticles with nonlinear dielectric core covered by metallic shell. Such nanoparticles support two surface plasmons of dipole type with different eigenfrequencies depending on volume portion of nonlinear dielectric. We demonstrate that giant enhancement of nonlinearity takes place under condition of double resonance when the fundamental frequency of light wave and its third harmonic simultaneously coincide or close to the frequencies of surface plasmons.