Terahertz to far-infrared emission by two-color, ultrashort optical pulses interacting with underdense helium gases at ultrahigh intensities (>10^{19} W/cm^{2}) is investigated by means of 3D particle-in-cell simulations. The terahertz field is shown to be produced by two mechanisms occurring sequentially, namely, photoionization-induced radiation (PIR) by the two-color pulse, and coherent transition radiation (CTR) by the wakefield-accelerated electrons escaping the plasma. We exhibit laser-plasma parameters for which CTR proves to be the dominant process, providing terahertz bursts with field strength as high as 100 GV/m and energy in excess of 10 mJ. Analytical models are developed for both the PIR and CTR processes, which correctly reproduce the simulation data.
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http://dx.doi.org/10.1103/PhysRevLett.120.144801 | DOI Listing |
Phys Rev Lett
April 2018
CEA, DAM, DIF, F-91297 Arpajon, France.
Terahertz to far-infrared emission by two-color, ultrashort optical pulses interacting with underdense helium gases at ultrahigh intensities (>10^{19} W/cm^{2}) is investigated by means of 3D particle-in-cell simulations. The terahertz field is shown to be produced by two mechanisms occurring sequentially, namely, photoionization-induced radiation (PIR) by the two-color pulse, and coherent transition radiation (CTR) by the wakefield-accelerated electrons escaping the plasma. We exhibit laser-plasma parameters for which CTR proves to be the dominant process, providing terahertz bursts with field strength as high as 100 GV/m and energy in excess of 10 mJ.
View Article and Find Full Text PDFPhys Rev Lett
July 2015
Max Planck Institute for the Science of Light, Guenther-Scharowsky-Strasse 1, 91058 Erlangen, Germany.
We propose a scheme for the emission of few-cycle dispersive waves in the midinfrared using hollow-core photonic crystal fibers filled with noble gas. The underlying mechanism is the formation of a plasma cloud by a self-compressed, subcycle pump pulse. The resulting free-electron population modifies the fiber dispersion, allowing phase-matched access to dispersive waves at otherwise inaccessible frequencies, well into the midinfrared.
View Article and Find Full Text PDFJ Chem Phys
September 2007
Chemical Resources Laboratory, Department of Electronic Chemistry, Interdisciplinary Graduate School of Science and Engineering, Tokyo Institute of Technology, 4259 Nagatsuta, Yokohama 226-8503, Japan.
IR spectra of phenol-Arn (PhOH-Arn) clusters with n=1 and 2 were measured in the neutral and cationic electronic ground states in order to determine the preferential intermolecular ligand binding motifs, hydrogen bonding (hydrophilic interaction) versus pi bonding (hydrophobic interaction). Analysis of the vibrational frequencies of the OH stretching motion, nuOH, observed in nanosecond IR spectra demonstrates that neutral PhOH-Ar and PhOH-Ar2 as well as cationic PhOH+-Ar have a pi-bound structure, in which the Ar atoms bind to the aromatic ring. In contrast, the PhOH+-Ar2 cluster cation is concluded to have a H-bound structure, in which one Ar atom is hydrogen-bonded to the OH group.
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