Magnetic and electric coherence in forward-and back-scattered electromagnetic waves by a single dielectric subwavelength sphere

Magnetodielectric small spheres present unusual electromagnetic scattering features, theoretically predicted a few decades ago. However, achieving such behaviour has remained elusive, due to the non-magnetic character of natural optical materials or the difficulty in obtaining low-loss highly permeable magnetic materials in the gigahertz regime. Here we present unambiguous experimental evidence that a single low-loss dielectric subwavelength sphere of moderate refractive index (n=4 like some semiconductors at near-infrared) radiates fields identical to those from equal amplitude crossed electric and magnetic dipoles, and indistinguishable from those of ideal magnetodielectric spheres. The measured scattering radiation patterns and degree of linear polarization (3-9 GHz/33-100 mm range) show that, by appropriately tuning the a/λ ratio, zero-backward ('Huygens' source) or almost zero-forward ('Huygens' reflector) radiated power can be obtained. These Kerker scattering conditions only depend on a/λ. Our results open new technological challenges from nano-and micro-photonics to science and engineering of antennas, metamaterials and electromagnetic devices. © 2012 Macmillan Publishers Limited. All rights reserved.This work was supported by the Spanish Ministerio de Ciencia e Innovación through grants: Consolider NanoLight (CSD2007-00046), FIS2009-13430-C01 and C02, FIS2010-21984, as well as by the Comunidad de Madrid (Microseres-CM, S2009/TIC-1476). B.G.-C. acknowledges his post-doctoral grant from the University of Cantabria, B.G.-C. and L.S.F.-P. acknowledge the financial support from the JAE-Program of the Spanish Council for Scientific Research (CSIC) co-funded by the European Social Fund (ESF).Peer Reviewe

Magnetic and electric coherence in forward- and back-scattered electromagnetic waves by a single dielectric subwavelength sphere

International audienceMagnetodielectric small spheres present unusual electromagnetic scattering features, theoretically predicted a few decades ago. However, achieving such behaviour has remained elusive, due to the non-magnetic character of natural optical materials or the difficulty in obtaining low-loss highly permeable magnetic materials in the gigahertz regime. Here we present unambiguous experimental evidence that a single low-loss dielectric subwavelength sphere of moderate refractive index (n¼4 like some semiconductors at near-infrared) radiates fields identical to those from equal amplitude crossed electric and magnetic dipoles, and indistinguishable from those of ideal magnetodielectric spheres. The measured scattering radiation patterns and degree of linear polarization (3-9 GHz/33-100mm range) show that, by appropriately tuning the a/l ratio, zero-backward ('Huygens' source) or almost zeroforward ('Huygens' reflector) radiated power can be obtained. These Kerker scattering conditions only depend on a/l. Our results open new technological challenges from nanoand micro-photonics to science and engineering of antennas, metamaterials and electromagnetic devices. DOI: 10.1038/ncomms2167