Plasmonic Helical Nanoantenna As a Converter between Longitudinal Fields and Circularly Polarized Waves

Abstract

A wide variety of optical applications and techniques require control of light polarization. So far, the manipulation of light polarization relies on components capable of interchanging two polarization states of the transverse field of a propagating wave (e.g., linear to circular polarizations, and vice versa). Here, we demonstrate that an individual helical nanoantenna is capable of locally converting longitudinally oriented confined near-fields into a circularly polarized freely propagating wave, and vice versa. To this end, the nanoantenna is coupled to cylindrical surface plasmons bound to the top interface of a thin gold layer. Helices of constant and varying pitch lengths are experimentally investigated. The reciprocal conversion of an incoming circularly wave into diverging cylindrical surface plasmons is demonstrated as well. Interconnecting circularly polarized optical waves (carrying spin angular momentum) and longitudinal near-fields provides a new degree of freedom in light polarization control.

Liquid crystal-templated chiral nanomaterials: from chiral plasmonics to circularly polarized luminescence

“…Chiral plasmonic nanomaterials with giant localized surface plasmon resonance (LSPR) have received increasingly significant attention for their emerging potential applications in diverse fields, such as negativerefractive-index materials, ultrasensitive biosensing, enantioselective analysis, and advanced light-polarization filters [130][131][132][133][134][135][136][137][138] . Compared to conventional top-down fabrication strategy [139][140][141][142] , the bottom-up self-assembly approach based on chiral soft templates allows for arbitrary and more tailorable structural geometries, thus enabling the development of highly complex chiral plasmonic nanomaterials with engineerable and dynamic chiroptical responses 41 .…”

Recent developments in the chiroptical properties of chiral plasmonic gold nanostructures: bioanalytical applications

“…The excitation of an L-handed helix with circular polarization generates a longitudinally oriented dipole containing the surface plasmons. This effect occurs in a broad wavelength range owing to the waveguide mode of surface plasmons propagating along the nanoantenna [31]. The stability of such nanoantenna is excellent.…”

“…The CD signal depends on the lattice plasmon polaritons. It creates an action potential at the sample surface, which is unique for a particular neurotoxin [31].…”

Self-assembled pagoda-like nanostructure-induced vertically stacked split-ring resonators for polarization-sensitive dichroic responses

“…Negative refractive index has been reported from stacked crescent-shaped structures in the broadband wavelength regime [ 15 ], and from two-dimensional perforated metal-dielectric stacks with a thickness much larger than the free-space wavelength [ 16 ]. In addition, strong chirality that allows transmission of specific circularly polarized light has been reported from chiral spiral structures [ 17 ].…”