Electric and magnetic dipolar response of germanium nanospheres: interference effects, scattering anisotropy, and optical forces

Raquel Gómez-Medina, Irene Suárez-Lacalle, Juan José Sáenz, Manuel Nieto-Vesperinas, Braulio García-Cámara, Francisco González, and Fernando Moreno

The coherent combination of electric and magnetic responses is the basis of the electromagnetic behavior of new engineered metamaterials. The basic constituents of their meta-atoms usually have metallic character and consequently high absorption losses. Based on standard “Mie” scattering theory, we found that there is a wide window in the near-infrared (wavelengths 1 to 3 μm), where light scattering by lossless submicrometer Ge spherical particles is fully described by their induced electric and magnetic dipoles. The interference between electric and magnetic dipolar fields is shown to lead to anisotropic angular distributions of scattered intensity, including zero backward and almost zero forward scattered intensities at specific wavelengths, which until recently was theoretically established only for hypothetically postulated magnetodielectric spheres. Although the scattering cross section at zero backward or forward scattering is exactly the same, radiation pressure forces are a factor of 3 higher in the zero forward condition.

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