講演情報
[15a-S4_201-4]Transverse spin from the transport of field singularities
〇Pin Christophe1, Sile Nic Chormaic1, Keiji Sasaki2 (1.OIST, 2.Hokkaido Univ.)
キーワード：
structured light、angular momentum、singularity
The transverse spin carried by structured light has been predicted and observed in various electromagnetic fields such as evanescent waves, interfering plane waves, and highly focused beams. Notably, it is generally admitted that the transverse spin of evanescent waves is governed by a right-handed spin-momentum locking effect, i.e. the direction of the transverse spin is given by the cross-product of the local momentum density (local phase gradient) and its decay direction. In this work, we show how left-handed spin-momentum locking can also take place in the near-field of plasmonic nanostructures when localized oscillating charges are separated by subwavelength nanogaps. Our results prove that the transverse spin of light can be understood as the topological consequence of the transport of field singularities. While singularities with positive vorticity (source, sink, circulation) give rise to right-handed spin-momentum locking, singularities with negative vorticity (saddle-point) result in left-handed spin-momentum locking.