scholarly journals “Perfect” Terahertz Vortex Beams Formed Using Diffractive Axicons and Prospects for Excitation of Vortex Surface Plasmon Polaritons

2021 ◽  
Vol 11 (2) ◽  
pp. 717
Author(s):  
Boris Knyazev ◽  
Valery Cherkassky ◽  
Oleg Kameshkov

Transformation of a Bessel beam by a lens results in the formation of a “perfect” vortex beam (PVB) in the focal plane of the lens. The PVB has a single-ring cross-section and carries an orbital angular momentum (OAM) equal to the OAM of the “parent” beam. PVBs have numerous applications based on the assumption of their ideal ring-type structure. For instance, we proposed using terahertz PVBs to excite vortex surface plasmon polaritons propagating along cylindrical conductors and the creation of plasmon multiplex communication lines in the future (Comput. Opt. 2019, 43, 992). Recently, we demonstrated the formation of PVBs in the terahertz range using a Bessel beam produced using a spiral binary silicon axicon (Phys. Rev. A 2017, 96, 023846). It was shown that, in that case, the PVB was not annular, but was split into nested spiral segments, which was obviously a consequence of the method of Bessel beam generation. The search for methods of producing perfect beams with characteristics approaching theoretically possible ones is a topical task. Since for the terahertz range, there are no devices like spatial modulators of light in the visible range, the main method for controlling the mode composition of beams is the use of diffractive optical elements. In this work, we investigated the characteristics of perfect beams, the parent beams being quasi-Bessel beams created by three types of diffractive phase axicons made of high-resistivity silicon: binary, kinoform, and “holographic”. The amplitude-phase distributions of the field in real perfect beams were calculated numerically in the approximation of the scalar diffraction theory. An analytical expression was obtained for the case of the binary axicon. It was shown that a distribution closest to an ideal vortex was obtained using a holographic axicon. The resulting distributions were compared with experimental and theoretical distributions of the evanescent field of a plasmon near the gold–zinc sulfide–air surface at different thicknesses of the dielectric layer, and recommendations for experiments were given.

2019 ◽  
Vol 43 (6) ◽  
pp. 992-1000 ◽  
Author(s):  
B.A. Knyazev ◽  
O.E. Kameshkov ◽  
A.K. Nikitin ◽  
V.S. Pavelyev ◽  
Yu.Yu. Choporova

Three optical systems employing diffractive optical elements to generate surface plasmon polaritons (SPP) with orbital angular momentum on axisymmetric conductors are considered. In all three systems, the incident radiation is first converted by binary spiral phase axicons into a set of plane waves converging to the optical axis. In the zone of intersection of these waves, a "twisted" Bessel beam is formed. By fitting the diameter of the first ring of the Bessel beam to the diameter of the cylindrical conductor, it is possible to generate a rotating SPP by the "end-fire coupling" method. The use of an additional lens makes it possible to convert the SPP-exciting Bessel beam into a vortex annular beam whose diameter is independent of the topological charge of the beam. In the third scheme, converging plane waves are “intercepted” by a cylindrical metal diffraction grating, which forms twisted SPPs on a cylindrical conductor connected to the grating. Examples of the possible use of the proposed systems in experiments on a terahertz free electron laser are presented.


2018 ◽  
Vol 28 (4) ◽  
pp. 30-38
Author(s):  
A. K. Nikitin ◽  
◽  
V. V. Gerasimov ◽  
B. A. Knyazev ◽  
I. Sh. Khasanov ◽  
...  

2004 ◽  
Vol 43 (12) ◽  
pp. 2409 ◽  
Author(s):  
Hiroshi Kano ◽  
Dai Nomura ◽  
Haruki Shibuya

2020 ◽  
Vol 8 (1) ◽  
pp. 3-26
Author(s):  
Boris A. Knyazev ◽  
Nikolay A. Vinokurov ◽  
Vasiliy V. Gerasimov ◽  
Yaroslav V. Getmanov ◽  
Yaroslav I. Gorbachyov ◽  
...  

A review of experiments in the field of photonics and plasmonics, recently performed with the Novosibirsk free electron laser (NovoFEL) is given. Parameters of NovoFEL radiation and user workstations are described. Considerable attention was paid to the development and testing of quasi-optical elements designed for this range and to methods for the formation of powerful beams of terahertz radiation with a given mode composition. The use of terahertz radiation in the spectroscopy of gases and semiconductors, in generation and study of surface plasmon polaritons, as well as the use of the latter for the study of surfaces and in communication applications is described.


2011 ◽  
Vol 181 (3) ◽  
pp. 305 ◽  
Author(s):  
V.B. Zon ◽  
B.A. Zon ◽  
V.G. Klyuev ◽  
A.N. Latyshev ◽  
D.A. Minakov ◽  
...  

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