Enhanced Terahertz Generation via Oblique Incidence of Unipolar Laser Pulses on Plasma

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Main Authors: P, Anjana K, Srivastav, Rohit Kumar, Kundu, Mrityunjay
Format: Preprint
Published: 2025
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author P, Anjana K
Srivastav, Rohit Kumar
Kundu, Mrityunjay
author_facet P, Anjana K
Srivastav, Rohit Kumar
Kundu, Mrityunjay
contents We investigate terahertz (THz) radiation generation at the vacuum-plasma interface driven by the oblique incidence of s-polarized Gaussian laser pulse(s) on a semi-infinite underdense plasma.~Extending beyond the conventional single-frequency bipolar pulse (B-pulse), this work focuses on leveraging two-color mixed-frequency pulse-- (M-pulse) excitation to enhance THz performance in terms of strength and broadening that can be tuned through controlled amplitude and phase of the constituent pulses of the M-pulse. A new expression for the ponderomotive force (PF) -- which acts as the main driver of THz radiation at the vacuum-plasma boundary -- is derived to capture the hitherto unexplored effects of phase asymmetry intrinsic to the M-pulse, in contrast to a single B-pulse where its phase is irrelevant. This PF formulation captures the underlying cycle-to-cycle symmetry-breaking for the M-pulse field, responsible for efficient THz emission. We demonstrate analytically that such M-pulses of the same total energy as a B-pulse may generate significantly enhanced PF, leading to THz yields several orders of magnitude higher. With a judicious choice of low-frequency to high-frequency ratio, the M-pulse configuration is shown to emerge as a highly efficient, phase-controllable driver of THz radiation and offers a promising route for optimizing THz source design via tailored two-color laser-plasma interactions.
format Preprint
id arxiv_https___arxiv_org_abs_2508_17963
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle Enhanced Terahertz Generation via Oblique Incidence of Unipolar Laser Pulses on Plasma
P, Anjana K
Srivastav, Rohit Kumar
Kundu, Mrityunjay
Plasma Physics
We investigate terahertz (THz) radiation generation at the vacuum-plasma interface driven by the oblique incidence of s-polarized Gaussian laser pulse(s) on a semi-infinite underdense plasma.~Extending beyond the conventional single-frequency bipolar pulse (B-pulse), this work focuses on leveraging two-color mixed-frequency pulse-- (M-pulse) excitation to enhance THz performance in terms of strength and broadening that can be tuned through controlled amplitude and phase of the constituent pulses of the M-pulse. A new expression for the ponderomotive force (PF) -- which acts as the main driver of THz radiation at the vacuum-plasma boundary -- is derived to capture the hitherto unexplored effects of phase asymmetry intrinsic to the M-pulse, in contrast to a single B-pulse where its phase is irrelevant. This PF formulation captures the underlying cycle-to-cycle symmetry-breaking for the M-pulse field, responsible for efficient THz emission. We demonstrate analytically that such M-pulses of the same total energy as a B-pulse may generate significantly enhanced PF, leading to THz yields several orders of magnitude higher. With a judicious choice of low-frequency to high-frequency ratio, the M-pulse configuration is shown to emerge as a highly efficient, phase-controllable driver of THz radiation and offers a promising route for optimizing THz source design via tailored two-color laser-plasma interactions.
title Enhanced Terahertz Generation via Oblique Incidence of Unipolar Laser Pulses on Plasma
topic Plasma Physics
url https://arxiv.org/abs/2508.17963