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. 2024 Nov 4;14:26587. doi: 10.1038/s41598-024-75832-0

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© The Author(s) 2024

Open Access This article is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License, which permits any non-commercial use, sharing, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if you modified the licensed material. You do not have permission under this licence to share adapted material derived from this article or parts of it. The images or other third party material in this article are included in the article’s Creative Commons licence, unless indicated otherwise in a credit line to the material. If material is not included in the article’s Creative Commons licence and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this licence, visit http://creativecommons.org/licenses/by-nc-nd/4.0/.

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Fig. 1 — Comparison of THz pulses generated by two-color laser pulses prepared with varying degrees of phase and intensity control. The spatiotemporal profiles for frequencies < 30 THz are displayed to the right of each optical configuration at three longitudinal locations in the far field. The circles below each configuration illustrate the evolution of the relative phase between the harmonics of the two-color pulse . (a) A phased-flying-focus pulse drives the conical emission of a half-cycle THz pulse over multiple dephasing lengths. The THz pulse is emitted into a single angle and has almost no angular dispersion. (b) A standard ultrashort-flying-focus pulse drives the conical emission of a multi-cycle THz pulse. Dephasing results in constructive interference at two characteristic angles and causes significant angular dispersion, which manifests in the near field as two diffuse rings. (c) A two-color laser pulse focused by an ideal lens also drives a multi-cycle THz pulse. In this case, the THz pulse evolves into a single diffuse ring in the near field, indicating both dephasing and complex evolution of the two-color laser pulse and resulting photocurrent. The near-field transverse profiles (red circles) are shown 1 m beyond the edge of the gas, and the white dashed lines in (a) and (b) mark the predictions of Eqs. (2) and (3). For ease of visualization, the optical configurations are displayed in transmission. In practice, only one harmonic is modified by the phaser.

Inline graphic — Comparison of THz pulses generated by two-color laser pulses prepared with varying degrees of phase and intensity control. The spatiotemporal profiles for frequencies < 30 THz are displayed to the right of each optical configuration at three longitudinal locations in the far field. The circles below each configuration illustrate the evolution of the relative phase between the harmonics of the two-color pulse . (a) A phased-flying-focus pulse drives the conical emission of a half-cycle THz pulse over multiple dephasing lengths. The THz pulse is emitted into a single angle and has almost no angular dispersion. (b) A standard ultrashort-flying-focus pulse drives the conical emission of a multi-cycle THz pulse. Dephasing results in constructive interference at two characteristic angles and causes significant angular dispersion, which manifests in the near field as two diffuse rings. (c) A two-color laser pulse focused by an ideal lens also drives a multi-cycle THz pulse. In this case, the THz pulse evolves into a single diffuse ring in the near field, indicating both dephasing and complex evolution of the two-color laser pulse and resulting photocurrent. The near-field transverse profiles (red circles) are shown 1 m beyond the edge of the gas, and the white dashed lines in (a) and (b) mark the predictions of Eqs. (2) and (3). For ease of visualization, the optical configurations are displayed in transmission. In practice, only one harmonic is modified by the phaser.