TY - JOUR

T1 - Broadband multimodal THz waveguides for efficient transfer of high-power radiation in space-confined conditions

AU - Melnikov, Anatoly R.

AU - Samsonenko, Arkady A.

AU - Getmanov, Yaroslav V.

AU - Shevchenko, Oleg A.

AU - Shevchenko, Darya A.

AU - Stepanov, Alexander A.

AU - Fedin, Matvey V.

AU - Yurkin, Maxim A.

AU - Veber, Sergey L.

N1 - Funding Information: The development of broadband multimodal THz waveguides and their characterization at the NovoFEL facility were funded by the Russian Science Foundation, grant number 17-13-01412. A.R.M. is grateful to the Council for Grants of the President of the Russian Federation for awarding a personal scholarship for Support of Young Researchers (Project No. SP-272.2021.5). We also thank Iryna Synelnyk for insightful discussion of waveguide theory. Publisher Copyright: © 2021 Elsevier Ltd Copyright: Copyright 2021 Elsevier B.V., All rights reserved.

PY - 2021/11

Y1 - 2021/11

N2 - Terahertz (THz) range, which lies between the microwave and infrared regions of the electromagnetic spectrum, presents a new frontier containing an abundance of technical applications and fundamental research problems. There are several challenges limiting the progress in the THz science and technology. One of them is the limited range of the guided-wave propagation of THz radiation, owing to the high loss from the finite conductivity of metals and the high absorption coefficient of dielectric materials in the THz range. In this work, we discuss the design and fabrication of multimodal hollow THz waveguides used at the X-band Electron Paramagnetic Resonance (EPR) endstation located at the Novosibirsk Free Electron Laser facility (NovoFEL). Experiments carried out at the EPR endstation are aimed to investigate the impact of THz and far infrared radiation on the spin system of different inorganic complexes and organic radicals. The EPR probehead and cryostat impose strict constraints on the possible ways of transferring the THz radiation to the sample, requiring the development, manufacturing, and characterization of specific waveguides. The proposed waveguides for X-band EPR measurements under THz radiation resemble hollow metal/dielectric waveguides. They have the shape of a hollow cylinder, tapering towards the end, with a silver-coated inner surface, and allow THz radiation to be transmitted over a distance of about 60 cm in a wide frequency range from THz to middle infrared. The waveguides performance was characterized at different frequencies of NovoFEL radiation and compared with numerical simulations. Following the requirements of polarization-sensitive EPR experiments, the waveguides were further modified by a miniature attachment, consisting of a polarizer, a semiconductor mirror, and a quarter-wave plate. The attachment allows preserving the initial polarization properties of THz radiation, turns its propagation vector, and creates the circular-polarized light irradiating the sample – all inside the limited volume of the EPR probehead.

AB - Terahertz (THz) range, which lies between the microwave and infrared regions of the electromagnetic spectrum, presents a new frontier containing an abundance of technical applications and fundamental research problems. There are several challenges limiting the progress in the THz science and technology. One of them is the limited range of the guided-wave propagation of THz radiation, owing to the high loss from the finite conductivity of metals and the high absorption coefficient of dielectric materials in the THz range. In this work, we discuss the design and fabrication of multimodal hollow THz waveguides used at the X-band Electron Paramagnetic Resonance (EPR) endstation located at the Novosibirsk Free Electron Laser facility (NovoFEL). Experiments carried out at the EPR endstation are aimed to investigate the impact of THz and far infrared radiation on the spin system of different inorganic complexes and organic radicals. The EPR probehead and cryostat impose strict constraints on the possible ways of transferring the THz radiation to the sample, requiring the development, manufacturing, and characterization of specific waveguides. The proposed waveguides for X-band EPR measurements under THz radiation resemble hollow metal/dielectric waveguides. They have the shape of a hollow cylinder, tapering towards the end, with a silver-coated inner surface, and allow THz radiation to be transmitted over a distance of about 60 cm in a wide frequency range from THz to middle infrared. The waveguides performance was characterized at different frequencies of NovoFEL radiation and compared with numerical simulations. Following the requirements of polarization-sensitive EPR experiments, the waveguides were further modified by a miniature attachment, consisting of a polarizer, a semiconductor mirror, and a quarter-wave plate. The attachment allows preserving the initial polarization properties of THz radiation, turns its propagation vector, and creates the circular-polarized light irradiating the sample – all inside the limited volume of the EPR probehead.

KW - Broadband multimodal THz waveguide

KW - EPR spectroscopy

KW - Free electron laser

KW - Hollow metal/dielectric waveguide

KW - Single-molecule magnet

KW - THz radiation

UR - http://www.scopus.com/inward/record.url?scp=85109631458&partnerID=8YFLogxK

U2 - 10.1016/j.optlastec.2021.107375

DO - 10.1016/j.optlastec.2021.107375

M3 - Article

AN - SCOPUS:85109631458

VL - 143

JO - Optics and Laser Technology

JF - Optics and Laser Technology

SN - 0030-3992

M1 - 107375

ER -