Transfer of orbital angular momentum of light to plasmonic excitations in metamaterials

Abstract

The emergence of the vortex beam with orbital angular momentum (OAM) has provided intriguing possibilities to induce optical transitions beyond the framework of the electric dipole interaction. The uniqueness stems from the OAM transfer from light to material, as demonstrated in electronic transitions in atomic systems. In this study, we report on the OAM transfer to electrons in solid-state systems, which has been elusive to date. Using metamaterials (periodically textured metallic disks), we show that multipolar modes of the surface electromagnetic excitations (so-called spoof localized surface plasmons) are selectively induced by the terahertz vortex beam. Our results reveal selection rules governed by the conservation of the total angular momentum, which is confirmed by numerical simulations. The efficient transfer of light’s OAM to elementary excitations in solid-state systems at room temperature opens up new possibilities of OAM manipulation.

Customizing the Topological Charges of Vortex Modes by Exploiting Symmetry Principles

“…For microwave applications, for the topological charges $$l\; = \; \pm 1$$, the circularly polarized waves can be used for the excitation, which exactly is what the spin–orbital conversion implies. [ 17,45 ] On the other hand, for applications where the excitations are realized by guided waves [ 29,31 ] (e.g., feeding networks at microwave frequencies and dielectric waveguides at optical frequencies), the first approach would need $$\hskip.001pt 4$$ phased wave ports, where the phases are determined by the irreps for the $${D_4}$$ group. The number of wave ports can quickly go up to $$M$$ for the $${D_M}$$ (or $${C_M}$$) group.…”

“…[ 3–4 ] Besides the use of vortex modes in the communication between two parties in each other's far field, another important application of vortex modes is to manipulate micro‐, nano‐, and atomic systems [ 11–13 ] in the near field of vortex mode generators, e.g., microparticle trapping, [ 11–12 ] discriminating extreme subwavelength particles, [ 13 ] and inducing optical transitions beyond electric dipole interactions. [ 14–17 ]…”

Spoof Localized Surface Plasmons for Sensing Applications

“…[ 134 ] Another advantage of OAM modes in resonators originates from the sharp resonance peaks, which are much more sensitive to chiral scatterers than circularly polarized beams in free‐space. Owing to its flexible geometry, spoof LSPs have been demonstrated to generate OAM states in radiative [ 135–137 ] and confined modes [ 122 ] within compacted sizes. As shown in Figure , periodically modulated corrugation are used to convert confined OAM modes in the spoof LSP resonator into radiative vortex beams.…”

Electromagnetic Wave Tunneling from Metamaterial Antiparallel Dipole Resonance

“…[5][6][7][8][9] Metamaterials, artificial materials composed of subwavelength structures, have shown characteristics such as negative refractive index, [10] negative permittivity, [11] high index, [12] chirality, [13] etc. Through metamaterial resonances, it is possible to manipulate the electric field, [14] magnetic field, [15] phase, [16] angular momentum, [17] etc. of light.…”