Ultra-broadband directive scattering of silicon nanoparticles in the optical range

Optical properties of high-refractive-index dielectric nanoparticles have attracted great scientific interest during the past several years [S. Jahani and Z. Jacob. Nat. Nanotechnol. 11, 23–36 (2016)]. These subwavelength... [ view full abstract ]

Optical properties of high-refractive-index dielectric nanoparticles have attracted great scientific interest during the past several years [S. Jahani and Z. Jacob. Nat. Nanotechnol. 11, 23–36 (2016)]. These subwavelength scatterers can support the excitation of electric and magnetic multipolar resonances which enhance the light-matter interaction in a controllable manner. Control can be organized by changing the nanoparticles size, geometry, and material. Directive scattering of standalone high-refractive nanoparticles is of high interest within the frameworks of modern nanophotonics. Nanoparticles with controllable scattering pattern can be used as effective re-translators of light, as meta-atoms of metamaterials and so on. One of the most known cases of nanoparticles’ directive scattering is a Kerker effect when most parts of energy scatter in the direction of incident light wave propagation, and backward scattering is almost zero [M. Kerker, D.-S. Wang and C. L. Giles. J. Opt. Soc. Am. 73, 765–767 (1983)]. Using nanoparticles with Kerker type scattering it is possible to construct fully invisible metasurfaces [M. Decker et al. Adv. Opt. Mater. 3, 813–820 (2015)]. Recently Kerker-type scattering was investigated for the silicon nanoparticles placed in the free space [S. Person et al. Nano Lett. 13, 1806–1809 (2013)] or on the substrate [K. V Baryshnikova, M. I. Petrov, V. E. Babicheva and P. A. Belov. Sci. Rep. 6, 22136 (2016)]. Kerker effect was achieved at certain frequencies where dipole moments of the nanoparticle are satisfied special conditions. Here we consider silicon nanoparticles placed in the homogeneous media with a refractive index different from the unity. Using method of multipole analysis, we show that for this system band of the effect can be effectively increased. Figure 1 illustrates how scattering pattern of cubical silicon nanoparticles changes in the optical spectral range. Multipole decomposition of scattering cross-section is also shown. Further, results of the experiment in the optical range, where silicon nanoparticles were placed in the glass media, is also discussed.