LP2N / LAPHIA SEMINAR - Thursday 16 May, 11:45, IOA - Juan José Sáenz

Asymmetry and Spin-Orbit interactions in light scattering by

high refractive index particles

Juan José Sáenz^,1,2,*

¹ Donostia International Physics Center, 20018 San Sebastian, Spain

² IKERBASQUE, Basque Foundation for Science, 48013 Bilbao, Spain

^* juanjo.saenz@dipc.org

Thursday 16 May 11:45 AM, IOA

Light spin-orbit angular momentum (AM) coupling phenomena are receiving an increasing interest in the analysis of scattering processes from sub-wavelength objects [1]. Spin-orbit interaction (SOI) of light can lead to optical mirages, i.e. a perceived displacement in the position of a particle due to the spiraling structure of the scattered light [2]. Here we will discuss the relevance of SOI phenomena in light scattering from subwavelength high refractive index (HRI) dielectric nanoparticles [3,4]

The optical properties of Silicon nanoparticles and other HRI materials are dominated by their dipolar electric and magnetic responses [5,6,7].  While for electric dipoles, the SOI induced optical mirage lead to subwavelength maximum displacements, we will see that the optical mirage depends strongly on the ratio between electric and magnetic dipolar responses. At the so-called first Kerker condition, there is a considerable enhancement (far above the wavelength) of the SOI  mirage related to the emergence of an optical vortex in the backscattering direction [3].

The remarkable angular dependence of these optical mirages and those of the intensity, degree of circular polarization (DoCP) and spin and orbital angular momentum of scattered photons are all linked, and fully determined, by the dimensionless “asymmetry parameter” g, being independent of the specific optical properties of the scatterer. Interestingly, for g not equal 0, the maxima of the optical mirage and angular momentum exchange take place at different scattering angles. We further we show that the g parameter is exactly half of the DoCP at a right-angle scattering, which opens the possibility to infer the whole angular properties of the scattered fields by a single far-field polarization measurement.

References

[1] K.Y. Bliokh et al., Nat. Photon. 9, 796 (2015)

[2] D. Haefner et al., Phys. Rev.Lett. 102, 123903 (2009)

[3] J. Olmos-Trigo et al., Phys. Rev. A 99, 013852 (2019)

[4] J. Olmos-Trigo et al., Opt. Lett.  44, 1762-1765(2019)

[5] A. García-Etxarri et al., Opt. Express 19, 4815 (2011)

[6] J.M. Geffrin et al., Nat. Commun. 3, 1171 (2012).

[7] A. I. Kuznetsov et al. Science 354, aag2472 (2016).