Circularly Polarized Scattering Radiation From a Silicon Nanosphere

Abstract A dielectric nanosphere with orthogonal electric dipole (ED) and magnetic dipole (MD) Mie resonances can be a nanoantenna radiating circularly polarized light in specific directions if the amplitudes and the phase relations are properly designed. First, theoretical calculations show that a silicon nanosphere illuminated with a linearly polarized plane wave radiates circularly polarized light at the wavelength in between the ED and MD resonances if the refractive index of a surrounding medium (n_m) is ≈1.3; the ellipticity of the scattered light can be >0.99 when n_m is in a 1.19–1.35 range. Size‐purified silicon nanospheres suspended in water (n_m = 1.33) are then prepared, and the angle‐ and circular‐polarization‐resolved scattering spectra are studied. It is experimentally demonstrated that circularly polarized light is radiated in specific directions under linearly polarized plane wave illumination. The results also show that the wavelength of the radiation of circularly polarized light can be controlled in the whole visible range by controlling the silicon nanosphere diameter in 100–200 nm range.