Hier finden Sie wissenschaftliche Publikationen aus den Fraunhofer-Instituten.

Probing the backscattering of TiO2 particles with vortex beams

: Zammbrana-Puyalto, Xavier; Vidal, Xavier; Molina-Terriza, Gabriel


Andrews, D.L. ; Society of Photo-Optical Instrumentation Engineers -SPIE-, Bellingham/Wash.:
Nanophotonics VIII : 6-10 April 2020, Online Only, France
Bellingham, WA: SPIE, 2020 (Proceedings of SPIE 11345)
ISBN: 978-1-5106-3462-6
ISBN: 978-1-5106-3463-3
Paper 1134507, 10 S.
Conference "Nanophotonics" <8, 2020, Online>
Fraunhofer IAF ()
Mie theory; multipoles; vortex beams; helicity; angular momentum; phase singularity; whispering gallery modes

We present a set of experiments in which the backscattering spectra of 4 μm single TiO2 particles are probed with circularly polarized vortex beams. The experiment is carried out with a tunable laser at λ = 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.