Optical magnetic response of laser fabricated Si nanoparticles

Femtosecond laser-induced transfer, developed for the generation of metallic micro- and nanoparticles [1], is applied to the fabrication of Si nanoparticles. This method allows controllable fabrication of high quality spherical Si nanoparticles with radii of 50-300 nm. Measured light scattering spectra of individual Si nanoparticles demonstrate strong resonant responses in the visible and near-infrared spectral ranges. Theoretical analysis on the basis of Mie theory with a multipole decomposition shows that the first two low-frequency resonances correspond to the magnetic dipole and electric dipole modes. At these resonances, Si nanoparticles generate scattered waves as magnetic and electric dipoles, respectively. Due to high Si permittivity, the magnetic dipole resonance is observed in the visible spectral range for Si nanoparticles with diameters of 100-200 nm. Magnetic optical response of non-spherical Si nanoparticles is also studied using numerical simulations [2]. Possibilities for the realization of isotropic optical metamaterials on the basis of the Si nanoparticles with negative permeability or negative refraction index in the visible spectral range are discussed.