We have obtained spectra of second-harmonic generation, third harmonic generation, and four-wave mixing from a fishnet metamaterial around its magnetic resonance. The resonant behaviors are distinctly different from those for ordinary materials. They
result from the fact that the resonance is plasmonic, and its enhancement appears through the local field in the nanostructure.
Optical modulation of the effective refractive properties of a fishnet metamaterial with a Ag/Si/Ag heterostructure is demonstrated in the near-IR range and the associated fast dynamics of negative refractive index is studied by pump-probe method. Ph
oto excitation of the amorphous Si layer at visible wavelength and corresponding modification of its optical parameters is found to be responsible for the observed modulation of negative refractive index in near-IR.
