Journal
NANOPHOTONICS VIII
Volume 11345, Issue -, Pages -Publisher
SPIE-INT SOC OPTICAL ENGINEERING
DOI: 10.1117/12.2555460
Keywords
Mie Theory; multipoles; vortex beams; helicity; angular momentum; phase singularity; whispering gallery modes
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Funding
- European Union's Horizon 2020 research and innovation programme under the Marie Sklodowska-Curie grant [795838]
- Marie Curie Actions (MSCA) [795838] Funding Source: Marie Curie Actions (MSCA)
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The experiment utilizes circularly polarized vortex beams to probe the backscattering spectra of single 4μm TiO2 particles, finding that vortex beams can tune backscattering and increase the conservation of helicity. The backscattering control method can be experimentally implemented in most microscopy setups and can also be used to excite single multipolar modes.
We present a set of experiments in which the backscattering spectra of 4 mu m single TiO2 particles are probed with circularly polarized vortex beams. The experiment is carried out with a tunable laser at lambda = 760 - 810nm. We observe that the use of vortex beams enables us to tailor the backscattering in different ways. Given a certain backscattering of a particle (induced by a Gaussian beam or a plane wave), we observe that vortex beams can tune it and sharpen it. Moreover, we also observe that the level of conservation of helicty can be increased thanks to the use of vortex beams. We explain the mechanisms that give rise to these effects using Mie Theory. Our method of backscattering control can be experimentally implemented in most of microscopy set-ups. In addition, if brought to its limits, the method can be used to excite single multipolar modes from spheres. We believe that our method could find application in the levitation of particles or the excitation of whispering gallery modes.
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