Generation of Terahertz Surface Plasmon Polaritons Using Nondiffractive Bessel Beams with Orbital Angular Momentum

Abstract

Bessel vortex beams with topological charges of l=±1 and l=±2 were produced in the terahertz spectral range from a free electron laser Gaussian beam (λ=141 μm) transformed using silicon binary diffractive optical elements. The spatial characteristics of the beams were obtained using a microbolometer array. A radius to path length ratio of 1:100 was achieved for nondiffractive beams with the average power of 30 W. Surface plasmon polaritons (SPPs) on gold-zinc-sulphide-air interfaces were generated due to diffraction of vortex beams on a sample edge. A new effect, a dependence of the efficiency of SPP generation on the direction of the azimuthal component of incident-radiation Poynting vector, was revealed.

Terahertz Bessel beams with orbital angular momentum: diffraction and interference

“…Recently, using radiation of the Novosibirsk free electron laser [9] and silicon binary spiral phase axicons, terahertz Bessel beams with OAM with topological charges 1 l r and 2 l r have been generated for the first time [7]. The intensity distributions of the beams formed by the axicons are in good agreement with the distributions calculated for Bessel beams, but they are identical for both left-handed and right-handed helicities.…”

“…To date, vortex beams were obtained in the range from radio frequencies [2] to the soft X-ray radiation [3]. Nevertheless, there are only five studies [4][5][6][7][8], in which vortex beams in the terahertz range have been generated.Recently, using radiation of the Novosibirsk free electron laser [9] and silicon binary spiral phase axicons, terahertz Bessel beams with OAM with topological charges 1 l r and 2 l r have been generated for the first time [7]. The intensity distributions of the beams formed by the axicons are in good agreement with the distributions calculated for Bessel beams, but they are identical for both left-handed and right-handed helicities.…”

“…To date, vortex beams were obtained in the range from radio frequencies [2] to the soft X-ray radiation [3]. Nevertheless, there are only five studies [4][5][6][7][8], in which vortex beams in the terahertz range have been generated.…”

Generating, Separating and Polarizing Terahertz Vortex Beams via Liquid Crystals with Gradient-Rotation Directors

“…Several methods, including spiral phase plates [14,15], computer-generated holograms [16,17], metasurfaces [18], and Pancharatnam-Berry phase optical elements (PBOEs) [19,20] have been implemented to generate THz vortex beams; however, they are either fixed without tunability and switchability, or suffer from low efficiency. Liquid crystal (LC) is an excellent candidate for THz devices [21][22][23][24][25][26][27][28].…”

Wave beams with orbital angular momentum: a step towards terahertz

“…Interest in beams with OAM [1,2], or "vortex beams," appeared shortly after the creation of lasers and increased after the publication of the article [3]. Vortex beams have been formed and investigated in the spectral range from X-ray to radio waves, but only a few publications are devoted to beams with OAM in the terahertz range (see [4] and references therein). In this paper we describe vortex Bessel beams with an average power of 25 W, obtained on the Novosibirsk free-electron laser (NovoFEL) [5].…”