Optical spectroscopy of single Si nanocylinders with magnetic and electric resonances

It is well-known from Mie theory that the first and second lowest resonances of dielectric particles correspond to the magnetic and electric dipole terms1. For higher refractive indexes, the quality factors of these Mie resonances and their light scattering efficiency increase. Due to these properties, the high-refractive index dielectric particles are considered as promising building blocks for the creation of metamaterials with negative effective permeability and permittivity2. Experimental demonstrations of dielectric metamaterials with strong magnetic and electric responses at microwave and mid-infrared frequencies were reported2,3. Recently, strong magnetic and electric dipole resonant responses of silicon spherical nanoparticles were predicted theoretically in the visible spectral range4 and in the infrared region5,6, and have been demonstrated experimentally7,8,9. Using these optical properties of Si nanoparticles new all-dielectric optical nanoantennas10,11,12 and optical metamaterials5,9,13,14 have been suggested. Recently, it has been theoretically15 and experimentally16 shown that the spectral positions of electric and magnetic dipole resonances of Si nanoparticles can be tuned by changing their shape. For example, it is possible to excite electric and magnetic dipole resonances at the same optical frequency for Si nanodisks by changing their aspect ratio15,16. This possibility allows controlling light scattering charcteristics by using Si nanodisks or nanocylinders with definite size parameters. This is one of the reasons why optical properties of cylindrical-shaped dielectric nanoparticles has been intensively studied recently16,17,18,19,20. It was experimentally demonstrated that a two-dimensional periodic array of silicon nanocylinders fabricated on a substrate and supporting Mie resonances yields almost zero total reflectance over the all visible spectral range17. Optical resonances of cylindrical Si nanoparticles located on different substrates and irradiated by normally incident light waves have been considered theoretically18. The influence of Mie resonances on the light absorption in periodic Si nanocylinders arrays has been experimentally demonstrated and studied in Ref. 20. In this paper, we investigate experimentally and theoretically optical resonant properties of single cylindrical Si nanoparticles located on a silica substrate and discuss the role played by excited multipole modes in their extinction and scattering spectra. Influences of light polarization and incident angle on the scattering diagram are studied as well.