Enhanced coherent transition radiation from midinfrared-laser-driven microplasmas
We present a particle-in-cell (PIC) analysis of terahertz (THz) radiation by ultrafast plasma currents driven by relativistic-intensity laser pulses. We show that, while the I [Formula: see text] product of the laser intensity I and the laser wavelength λ plays the key role in the energy scaling of...
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Published in | Scientific reports Vol. 12; no. 1; pp. 7660 - 12 |
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Main Authors | , |
Format | Journal Article |
Language | English |
Published |
England
Nature Publishing Group
10.05.2022
Nature Publishing Group UK Nature Portfolio |
Subjects | |
Online Access | Get full text |
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Summary: | We present a particle-in-cell (PIC) analysis of terahertz (THz) radiation by ultrafast plasma currents driven by relativistic-intensity laser pulses. We show that, while the I
[Formula: see text] product of the laser intensity I
and the laser wavelength λ
plays the key role in the energy scaling of strong-field laser-plasma THz generation, the THz output energy, W
, does not follow the I
[Formula: see text] scaling. Its behavior as a function of I
and λ
is instead much more complex. Our two- and three-dimensional PIC analysis shows that, for moderate, subrelativistic and weakly relativistic fields, W
(I
[Formula: see text]) can be approximated as (I
λ
)
, with a suitable exponent α, as a clear signature of vacuum electron acceleration as a predominant physical mechanism whereby the energy of the laser driver is transferred to THz radiation. For strongly relativistic laser fields, on the other hand, W
(I
[Formula: see text]) closely follows the scaling dictated by the relativistic electron laser ponderomotive potential [Formula: see text], converging to W
∝ [Formula: see text] for very high I
, thus indicating the decisive role of relativistic ponderomotive charge acceleration as a mechanism behind laser-to-THz energy conversion. Analysis of the electron distribution function shows that the temperature T
of hot laser-driven electrons bouncing back and forth between the plasma boundaries displays the same behavior as a function of I
and λ
, altering its scaling from (I
λ
)
to that of [Formula: see text], converging to W
∝ [Formula: see text] for very high I
. These findings provide a clear physical picture of THz generation in relativistic and subrelativistic laser plasmas, suggesting the THz yield W
resolved as a function of I
and λ
as a meaningful measurable that can serve as a probe for the temperature T
of hot electrons in a vast class of laser-plasma interactions. Specifically, the α exponent of the best (I
λ
)
fit of the THz yield suggests a meaningful probe that can help identify the dominant physical mechanisms whereby the energy of the laser field is converted to the energy of plasma electrons. |
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Bibliography: | ObjectType-Article-1 SourceType-Scholarly Journals-1 ObjectType-Feature-2 content type line 23 |
ISSN: | 2045-2322 2045-2322 |
DOI: | 10.1038/s41598-022-10614-0 |