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1Generation of terahertz multimode vortex surface plasmon
polariton
N. Osintseva1*, V. Gerasimov12**, V. Pavelyev34, Yu. Choporova1, K. Tukmakov3, B. Knyazev
1-Budker Institute of Nuclear Physics SB RAS, 11 Ac. Lavrentieva Ave., Novosibirsk 630090, Russia 2- Novosibirsk State University, 1 Pirogova St., Novosibirsk 630090, Russia 3- Samara National Research University, 34 Moskovskoye Shosse, Samara 443086, Russia 4- Image Processing Systems Institute, NRC "Kurchatov Institute", 151 Molodogvardeyskaya St.,
Samara 443001, Russia
* [email protected] ** [email protected]
In today's world, the terahertz range is attracting increasing interest from researchers, especially with the active shift towards the sub-terahertz frequency range (120-350 GHz) in wireless networks, such as 6G data transmission. The use of terahertz vortex Bessel beams (VBBs) with multiplexing capabilities can greatly enhance data capacity. VBBs also have applications in wired data transmission.
The waveguide approach for data transmission in miniature integrated optical devices in the terahertz region is currently under development. However, there is an alternative solution that involves excitation of surface waves (surface plasmon polaritons, SPPs) on the surface of an axisymmetric conductor by perfect vortex Bessel beams through an end-fire coupling technique. Previous research [1] has demonstrated the generation of vortex SPPs on a cylindrical line, their transmission along the line, and diffraction into a vortex free-wave with the same topological charge.
In this study, we present experimental results on the generation of multimode vortex surface plasmon polaritons on a metallic cylinder coated with a 1-^m thick zinc sulfide layer, using a 130 ^m radiation of the Novosibirsk Free Electron Laser. Two VBBs with the topological charges 3 and 9 were generated in the arms of a tilted Mach-Zehnder interferometer (60° to the optical axis of the input beam) using spiral phase binary axicons. A combined beam at the interferometer output formed in the back focal plane of a lens a two-mode perfect vortex beam, which was used for the excitation of vortex plasmons with the same topological charges. Recording the output radiation with the optical system shown in Fig. 1, we investigated the possibility to identify multiplex signals passing the system and use it in data transmission applications. The experiments were carried out at the Novosibirsk free electron laser, which is a part of the Shared Research Facility "Siberian Synchrotron and Terahertz Radiation Center".
/=-9&/=+3
Fig. 1. Experimental scheme for vortex multimode SPP generation in Mach-Zehnder interferometer: BS - beamsplitter, D - iris diaphragm, M - flat mirror, DOE - spiral binary axicons, L - kinoform lens with f=80 mm with ^=130 ^m, ATL - axisymmetric transmission line, Detector - microbolometer array.
[1] V. Gerasimov, et al, Vortex surface plasmon polaritons on a cylindrical waveguide: Generation, propagation, and diffraction, Journal of Optics, vol. 23, pp. 10LT01, (2021).
