In this work we demonstrate the generation of two intense, ultrafast laser pulses that allow a controlled interferometric measurement of higher harmonic generation pulses with 12.8 attoseconds in resolution (half the atomic unit of time) and a precision as low as 680 zeptoseconds (10 seconds). We create two replicas of a driving femtosecond pulse which share the same optical path except at the focus where they converge to two foci. An attosecond pulse train emerges from each focus through the process of high harmonic generation. The two attosecond pulse trains from each focus interfere in the far field producing a clear interference pattern in the extreme ultraviolet region. By controlling the relative optical phase (carrier envelope phase for pulsed fields) between the two driving laser pulses we are able to actively influence the delay between the pulses and are able to perform very stable and precise pump-probe experiments. Because of the phase shaping operation occurs homogeneously across the entire spatial profile, we effectively create two indistinguishable intense laser pulses or a common path interferometer for attosecond pulses. Commonality across the two beams means that they are extremely stable to environmental and mechanical fluctuations up to a Rayleigh range from the focus. In our opinion this represents an ideal source for homodyne and heterodyne spectroscopic measurements with sub-attosecond precision.
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http://dx.doi.org/10.1364/OE.27.022960 | DOI Listing |
Sci Rep
January 2025
Jilin Key Laboratory of Solid-State Laser Technology and Application, School of Science, Changchun, 130022, Jilin, China.
The response mechanism of a Four-Quadrant Photodetector (QPD) in an experimental setting was studied by irradiating a single QPD cell with a millisecond-pulsed laser. The response signal of the irradiated QPD cell varied with energy flux, pulse width, and applied bias, and comprised four main stages: an initial stage, decreasing barrier stage, holding stage, and recovery stage. Not only was the response signal of the irradiated cell affected by laser irradiation, but also the responses of the other three cells.
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January 2025
Los Alamos National Laboratory, Los Alamos, NM, 87544, USA.
Detecting shielded special nuclear material, such as nuclear explosives, is a difficult challenge pursued by non-proliferation, anti-terrorism, and nuclear security programs worldwide. Interrogation with intense fast-neutron pulses is a promising method to characterize concealed nuclear material rapidly but is limited by suitable source availability and proven instrumentation. In this study we have pioneered a demonstration of such an interrogation method using a high-intensity, short-pulse, laser-driven neutron source that offers potential benefits compared to conventional neutron sources.
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December 2024
Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA.
We measure the high-intensity laser propagation throughout meter-scale, channel-guided laser-plasma accelerators by adjusting the length of the plasma channel on a shot-by-shot basis, showing high-quality guiding of 500 TW laser pulses over 30 cm in a hydrogen plasma of density n_{0}≈1×10^{17} cm^{-3}. We observed transverse energy transport of higher-order modes in the first ≈12 cm of the plasma channel, followed by quasimatched propagation, and the gradual, dark-current-free depletion of laser energy to the wake. We quantify the laser-to-wake transfer efficiency limitations of currently available petawatt-class lasers and demonstrate via simulation how control over the laser mode can significantly improve beam parameters.
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December 2024
European Synchrotron Radiation Facility (ESRF), 71 Avenue des Martyrs, Grenoble, CS 40220, 38043, France.
Studying the properties and phase diagram of iron at high-pressure and high-temperature conditions has relevant implications for Earth's inner structure and dynamics and the temperature of the inner core boundary (ICB) at 330 GPa. Also, a hexagonal-closed packed to body-centered cubic (bcc) phase transition has been predicted by many theoretical works but observed only in a few experiments. The recent coupling of high-power laser with advanced x-ray sources from synchrotrons allows for novel approaches to address these issues.
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December 2024
Institute of Atomic and Molecular Physics, Jilin University, Changchun 130012, China.
We have observed the laser-assisted dynamic interference in the electron spectra triggered by attosecond pulse trains. The fingerprints of finer interference fringes, much smaller than the laser photon energy, have been clearly identified experimentally. Our measurements are successfully reproduced by theoretical simulations utilizing the numerical solution to the time-dependent Schrödinger equation and the strong-field approximation.
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