M.Sc Student | Nechayev Sergey |
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Subject | Plasmonic Aharonov-Bohm Effect: Optical Spin as the Magnetic Flux Parameter |

Department | Department of Nanoscience and Nanotechnology |

Supervisor | Professor Erez Hasman |

Full Thesis text |

Spinoptics is a promising area of research that proposes a new generation of optical elements for nano-photonic applications. These elements can manipulate the angular momentum (AM) state of light and produce an optical spin-orbit interaction (SOI).

The angular momentum of an optical beam comprises the intrinsic component, the spin (polarization helicity), associated with the handedness of the circular polarization, and the extrinsic component, orbital AM (OAM), associated with a spiral phase front. Optical spin-orbit interaction occurs when intrinsic spin and extrinsic (orbital/linear) momentum of the electromagnetic field are coupled.

In general, SOI lies in the origin of various remarkable effects in diverse fields of physics and at different scales, ranging from stellar objects to fundamental particles. In these effects, the SOI implies a correction of the generalized momentum, thereby imposing a dispersion relation modification. This modification is manifested by a spin-dependent geometric phase which may result in a spin symmetry breaking even in structures with full rotational symmetry. Such phenomena as Aharonov-Bohm effect and Rashba splitting arise due to appearance of the geometric Berry.

We demonstrated a plasmonic equivalent of the Aharonov-Bohm (AB) effect and measured a spin-dependent phase dislocation in the near-field due to scattering of surface plasmons from a rotationally symmetric topological defect. The dislocation strength was shown to be equal to the incident optical spin in a manner similar to the AB wavefunction dislocation strength being equal to the magnetic flux parameter. Moreover, we experimentally demonstrated that the surface plasmon polariton (SPP) wave dislocation is independent on the incident wavelength, therefore verifying the geometric nature of the phenomenon. Our analysis sheds light on the intriguing role of optical angular momentum in scattering from topological defects and the analogy presented in this work provides an additional insight into a mechanism of SOI.