Experimental observation of transverse spin of plasmon polaritons in a single-crystalline silver nanowire

Abstract

We report the experimental observation of the transverse spin and associated spin-momentum locking of surface plasmon polaritons (SPPs) excited in a plasmonic single crystalline silver nanowire (AgNW). In contrast to the SPPs excited in metal films, the electromagnetic field components of the evanescent SPP mode propagating along the long axis ($x$ axis) of the NW can decay along two longitudinal planes ($x$-$y$ and $x$-$z$ planes), resulting in two orthogonal transverse spin components ($s_z$ and $s_y$). Analysis of the opposite circular polarization components of the decaying SPP mode signal in the longitudinal plane ($x$-$y$) reveals spin dependent biasing of the signal and hence the existence of transverse spin component ($s_z$). The corresponding transverse spin density ($s_3$) in the Fourier plane reveals spin-momentum locking, where the helicity of the spin is dictated by the wave-vector components of the SPP evanescent wave. Further, the results are corroborated with three-dimensional numerical calculations. The presented results showcase how a chemically prepared plasmonic AgNW can be harnessed to study optical spins in evanescent waves, and can be extrapolated to explore sub-wavelength effects including directional spin coupling and optical nano-manipulation.

arXiv comment25 pages, 8 figures

References in corpus (29)

• Spin-orbit interactions of light
• A single-photon transistor using nano-scale surface plasmons
• Transverse and longitudinal angular momenta of light
• Quantum spin Hall effect of light
• Chiral nanophotonic waveguide interface based on spin-orbit coupling of light
• Extraordinary momentum and spin in evanescent waves
• Does a Surface Polariton Have Spin?
• Internal flows and energy circulation in light beams
• Universal spin-momentum locking of evanescent waves
• Nanoscale chiral valley-photon interface through optical spin-orbit coupling
• Measuring the Transverse Spin Density of Light
• Transverse spin and momentum in two-wave interference
• Direct measurements of the extraordinary optical momentum and transverse spin-dependent force using a nano-cantilever
• Janus and Huygens' dipolar sources for near-field directionality
• Polarization Controlled Directional Scattering for Nanoscopic Position Sensing
• Near-to-far field transformations for radiative and guided waves
• Spin-orbit interaction of light induced by transverse spin angular momentum engineering
• Comparative analysis of imaging configurations and objectives for Fourier microscopy
• Transverse spin dynamics of light: the generalized spin-momentum locking for structured guided modes
• Paraxial Light Beams with Angular Momentum
• Relativistic Hall Effect
• Transverse Chiral Optical Forces by Chiral Surface Plasmon Polaritons
• Spin-Momentum Locking in the Near Field of Metal Nanoparticles
• Spin angular momentum in planar and cylindrical waveguides induced by transverse confinement and intrinsic helicity of guided light
• Spin-Hall effect in the scattering of structured light from plasmonic nanowire
• Focused linearly-polarized light scattering from a silver nanowire: Experimental characterization of optical spin-Hall effect
• Momentum-resolved surface enhanced Raman scattering from a nanowire-nanoparticle junction cavity
• Spectral singularity enhances transverse spin
• Spin selective scattering modes in random anisotropy optical medium