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The low-order harmonic generation induced by a strong laser field produces a bright, ultrashort, supercontinuum radiation ranging from the terahertz to ultraviolet band. By controlling the phase-delay and ellipticity of the bi-chromatic laser fields, the third harmonic generation is experimentally and theoretically investigated for elucidating the mechanism of the low-order harmonics. The third harmonic generation is found to be strongly suppressed in the counter-rotating bi-chromatic laser field due to the selection rule for harmonic emissions. The continuum-continuum transition in the strong field approximation is extended to explain the third harmonic generation as a function of the phase delay and ellipticity of the bi-chromatic laser fields. Compared with the semi-classical photocurrent model, the continuum-continuum transition on the basis of quantum-mechanical treatment achieves better agreement with the experimental observations. Our work indicates that the overlapping in continuum states via different quantum paths of a single electron plays a role in low-order harmonics generation under elliptical bi-chromatic laser fields.
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http://dx.doi.org/10.1364/OE.427232 | DOI Listing |
Phys Rev Lett
August 2025
The Pennsylvania State University, University Park, Pennsylvania 16802, USA.
Simulating large-scale lattice dynamics remains a long-standing challenge in condensed matter and materials science, where mechanical and thermal behaviors arise from coupled vibrational modes. We introduce a quantum algorithm that reformulates general harmonic lattice dynamics as a time-dependent Schrödinger equation governed by a sparse, Hermitian Hamiltonian. This enables the use of Hamiltonian simulation techniques on quantum devices, offering exponential speedup in the number of atoms N.
View Article and Find Full Text PDFPhys Rev Lett
August 2025
University of Delaware, Department of Physics and Astronomy, Newark, Delaware 19716, USA.
Ultrafast light-driven strongly correlated antiferromagnetic insulators, such as prototypical NiO with a large Mott energy gap ≃4 eV, have recently attracted experimental attention using photons of both subgap [H. Qiu et al., Nat.
View Article and Find Full Text PDFBeilstein J Nanotechnol
September 2025
B. I. Stepanov Institute of Physics, National Academy of Sciences of Belarus, 220072 Minsk, Belarus.
In this study, silicon nanoparticles (NPs) were produced by pulsed laser ablation in a liquid, aiming to investigate the influence of a laser beam profile on the properties of the resultant NPs. Morphology, inner structure, and phase composition of the formed NPs were characterized by means of ultraviolet-visible spectroscopy, high-resolution transmission electron microscopy, and Raman and photoluminescence spectroscopies, and the correlation of the NP properties with the laser beam profile was studied. Three different beam profiles were selected, namely, a Bessel beam produced using an axicon, an annular profile formed using a combination of an axicon and a converging lens, and a Gaussian beam focused on the surface of a Si target using the same converging lens.
View Article and Find Full Text PDFIEEE Trans Biomed Eng
September 2025
Objective: Diffusion magnetic resonance imaging (dMRI) often suffers from low spatial and angular resolution due to inherent limitations in imaging hardware and system noise, adversely affecting the accurate estimation of microstructural parameters with fine anatomical details. Deep learning-based super-resolution techniques have shown promise in enhancing dMRI resolution without increasing acquisition time. However, most existing methods are confined to either spatial or angular super-resolution, disrupting the information exchange between the two domains and limiting their effectiveness in capturing detailed microstructural features.
View Article and Find Full Text PDFJ Chem Phys
September 2025
Jülich Centre for Neutron Science (JCNS-1), Forschungszentrum Jülich GmbH, 52428 Jülich, Germany.
The static and dynamic properties of a cyclic Rouse chain modified by the introduction of an effective, spherically symmetric, attracting potential of entropic nature are studied. It is shown that a relatively weak potential can lead to a strong contraction of the polymer chain: the radius of gyration becomes much smaller compared to the size of the free cyclic chain. The pronounced decrease in the terminal relaxation time of cyclic macromolecules in the presence of a harmonic potential compared to the Rouse relaxation time leads to a lengthening of the time interval for the transition to the normal, i.
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