Helicity locking in light emitted from a plasmonic nanotaper

Abstract

Surface plasmon waves carry an intrinsic transverse spin, which is locked to its propagation direction. Apparently, when a singular plasmonic mode is guided on a conic surface this spin-locking may lead to a strong circular polarization of the far-field emission. Specifically, an adiabatically tapered gold nanocone guides an a priori excited plasmonic vortex upwards where the mode accelerates and finally beams out from the tip apex. The helicity of this beam is shown to be single-handed and stems solely from the transverse spin-locking of the helical plasmonic wave-front. We present a simple geometric model that fully predicts the emerging light spin in our system. Finally we experimentally demonstrate the helicity-locking phenomenon by using accurately fabricated nanostructures and confirm the results with the model and numerical data.

arXiv comment15 pages, 4 figures

References in corpus (8)

• Spin-orbit interactions of light
• Does a Surface Polariton Have Spin?
• Measuring the Transverse Spin Density of Light
• Direct measurements of the extraordinary optical momentum and transverse spin-dependent force using a nano-cantilever
• Weak Measurements of Light Chirality with a Plasmonic Slit
• Circular polarization in the optical afterglow of GRB 121024A
• Unidirectional sub-diffraction waveguiding based on optical spin-orbit coupling in subwavelength plasmonic waveguides
• Beaming of helical light from plasmonic vortices via adiabatically tapered nanotip