https://doi.org/10.1140/epjp/s13360-023-04511-2
Regular Article
Multiresonance terahertz radiation and its tuning by laser irradiation of medium containing core-shell nanoparticles
Plasma Waves and Particle Acceleration Laboratory, Department of Physics, Indian Institute of Technology, 110 016, Delhi, New Delhi, India
Received:
8
May
2023
Accepted:
23
September
2023
Published online:
9
October
2023
Two skew-cosh-Gaussian laser beams of slightly different frequencies and wavenumbers are used to achieve beating in a medium that contains spherical and cylindrical core-shell nanoparticles (NPs) and is under the action of an external periodic electrostatic field. The gradient in the intensity of the incident laser beams and pairing of their electric fields with the external periodic field are responsible for the generation of three components of the ponderomotive force, leading to three kinds of nonlinear currents due to nonlinear velocity of the electron clouds of the NPs because of the ponderomotive force. These currents result in the generation of multiresonance Terahertz (THz) field, termed as beating-enabled THz field (
) and induced THz fields (
and 
). The periodicities of density ripples and external electrostatic field aid in the complete transfer of momentum from the laser photons to the electron clouds of the NPs in addition to the frequency resonance, help achieving the multiple resonance conditions. In order to consider the realistic situation, the restoring forces and damping constants according to the shape of the nanoparticles are also considered for accurate THz emission. A comparative study between the ponderomotive forces and corresponding THz fields is performed to analyse the behaviour of the induced fields. The role of the core-shell nanoparticles in terms of their different aspect ratios and core-to-shell radius ratios and of the external field is uncovered in enhancing and tuning of the THz radiation in addition to raising the amplitude of secondary THz peak achieved due to transverse plasmon resonance. The emitted multiresonance and tunable THz radiation would be useful in the effective diagnosis of the damaged tissues located at different positions in the human body in a regulated and efficient manner for their medical treatments.
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© The Author(s), under exclusive licence to Società Italiana di Fisica and Springer-Verlag GmbH Germany, part of Springer Nature 2023. Springer Nature or its licensor (e.g. a society or other partner) holds exclusive rights to this article under a publishing agreement with the author(s) or other rightsholder(s); author self-archiving of the accepted manuscript version of this article is solely governed by the terms of such publishing agreement and applicable law.
