| Issue |
J. Eur. Opt. Society-Rapid Publ.
Volume 20, Number 2, 2024
THz imaging
|
|
|---|---|---|
| Article Number | 39 | |
| Number of page(s) | 10 | |
| DOI | https://doi.org/10.1051/jeos/2024042 | |
| Published online | 25 November 2024 | |
Research Article
Frequency-resolved measurement of two-color air plasma terahertz emission
1
Institute of Post-LED Photonics, Tokushima University, 2-1 Minami-Josanjima, Tokushima 770-8506, Japan
2
CNRS LOMA, UMR 5798, Bordeaux University, Talence, France
* Corresponding author: emmanuel.abraham@u-bordeaux.fr
Received:
1
July
2024
Accepted:
14
October
2024
We investigated the far-field terahertz beam profile generated from an air plasma induced by two-color femtosecond laser pulses. Under our experimental conditions (filament length shorter than the dephasing length between the two-color pulses), using electro-optic sampling in both ZnTe (0.2–2.2 THz) and GaP (0.4–6.8 THz) crystals, and ultra-broadband ABCD technique (1–17.5 THz), we determined that the THz beam exhibits a unimodal beam pattern below 4 THz and a conical one above 6 THz. This experimental finding is consistent with theoretical studies based on the unidirectional pulse propagation equation, which predict the transition of THz emission from a flat-top profile to a conical one due to the destructive interference of THz waves emitted from the plasma filament. Our results also underscore the importance of accounting for experimental artifacts, such as photo-excited losses in silicon resulting in on-axis THz absorption along with the influence of drilled mirrors, in characterizing the complex spatial and frequency-dependent behavior of two-color plasma-induced terahertz emission.
Key words: Terahertz emission / Two-color laser-induced plasma / Air plasma filament / Beam profile / Electro-optic sampling / ABCD technique
© The Author(s), published by EDP Sciences, 2024
This is an Open Access article distributed under the terms of the Creative Commons Attribution License (https://creativecommons.org/licenses/by/4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
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