Tailoring multipolar Mie scattering with helicity and angular momentum

TL;DR

This paper experimentally explores how the angular momentum and helicity of light influence the scattering behavior of spherical particles, revealing that these parameters can tailor multipolar resonances and scattering spectra.

Contribution

It demonstrates the control of multipolar modes and spectral features in light scattering by manipulating the angular momentum and helicity of incident beams.

Findings

Spectral behavior depends on angular momentum and helicity.

High angular momentum beams induce complex multipolar modes.

Tailoring modes causes spectral shifts and narrowing.

Abstract

Linear scattering processes are usually described as a function of the parameters of the incident beam. The wavelength, the intensity distribution, the polarization or the phase are among them. Here, we discuss and experimentally demonstrate how the angular momentum and the helicity of light influence the light scattering of spherical particles. We measure the backscattering of a $4\mu m$ TiO$_2$ single particle deposited on a glass substrate. The particle is probed at different wavelengths by different beams with total angular momenta ranging from $-8$ to $+8$ units. It is observed that the spectral behavior of the particle is highly dependent on the angular momentum and helicity of the incoming beam. While some of the properties of the scattered field can be described with a simple resonator model, the scattering of high angular momentum beams requires a deeper understanding of the multipolar modes induced in the sphere. We observe that tailoring these induced multipolar modes can cause a shift and a spectral narrowing of the peaks of the scattering spectrum. Furthermore, specific combinations of helicity and angular momentum for the excitation lead to differences in the conservation of helicity by the system, which has clear consequences on the scattering pattern.