Abstract-Guiding and emission of milijoule single-cycle THz pulse from laser-driven wire-like targets

Yushan Zeng, Chuliang Zhou, Liwei Song, Xiaoming Lu, Zhongpeng Li, Yingying Ding, Yafeng Bai, Yi Xu, Yuxin Leng, Ye Tian, Jiansheng Liu, Ruxin Li, and Zhizhan Xu

Simulated THz radiation pattern from tip and wire targets. (a) Radiation power pattern from the tip target. The blue line indicates the main lobe direction (which is 17° when 0.18 THz frequency is simulated). The inset represents a frame of electric vector distribution in the transverse cross section. (b) Left: 3D profile of the 0.18 THz frequency radiation power emitted from a 200 µm diameter, 60 mm long wire with a 1 mm diameter semicircle presented at end. Right: A slice distribution of the radiation intensity cutted at 𝜑$\phi$ = 90° (y-z plane), showing asymmetric energy distribution caused by the wire curvature. (c) Simulated electric field evolution (in y-z plane) respectively from the tip target (upper row) and wire (lower row, without curvature at wire end) in time domain. The t=0 has been set to the time when the field front arrives the waveguide end.

https://www.osapublishing.org/oe/abstract.cfm?uri=oe-28-10-15258

The miscellaneous applications of terahertz have called for an urgent demand of a super intense terahertz source. Here, we demonstrate the capability of femtosecond laser-driven wires as an efficient ultra-intense terahertz source using 700 mJ laser pulses. When focused onto a wire target, coherent THz generation took place in the miniaturized gyrotron-like undulator where emitted electrons move in the radial electric field spontaneously created on wire surface. The single-cycle terahertz pulse generated from the target is measured to be radially polarized with a pulse energy of a few milijoule. By further applying this scheme to a wire-tip target, we show the near field of the 500 nm radius apex could reach up to 90 GV/m. This efficient THz energy generation and intense THz electric field mark a substantial improvement toward ultra-intense terahertz sources.

© 2020 Optical Society of America under the terms of the OSA Open Access Publishing Agreement

Abstract-Molecular polarizability anisotropy of liquid water revealed by terahertz-induced transient orientation

Peter Zalden, Liwei Song, Xiaojun Wu, Haoyu Huang, Frederike Ahr, Oliver D. Mücke, Joscha Reichert, Michael Thorwart, Pankaj Kr. Mishra, Ralph Welsch, Robin Santra, Franz X. Kärtner, Christian Bressler,

https://www.nature.com/articles/s41467-018-04481-5

Reaction pathways of biochemical processes are influenced by the dissipative electrostatic interaction of the reagents with solvent water molecules. The simulation of these interactions requires a parametrization of the permanent and induced dipole moments. However, the underlying molecular polarizability of water and its dependence on ions are partially unknown. Here, we apply intense terahertz pulses to liquid water, whose oscillations match the timescale of orientational relaxation. Using a combination of terahertz pump / optical probe experiments, molecular dynamics simulations, and a Langevin dynamics model, we demonstrate a transient orientation of their dipole moments, not possible by optical excitation. The resulting birefringence reveals that the polarizability of water is lower along its dipole moment than the average value perpendicular to it. This anisotropy, also observed in heavy water and alcohols, increases with the concentration of sodium iodide dissolved in water. Our results enable a more accurate parametrization and a benchmarking of existing and future water models.

Abstract-Waveform-Controlled Terahertz Radiation from the Air Filament Produced by Few-Cycle Laser Pulses

http://arxiv.org/abs/1204.1860

Ya Bai, Liwei Song, Rongjie Xu, Chuang Li, Peng Liu, Zhinan Zeng, Zongxin Zhang, Haihe Lu, Ruxin Li, Zhizhan Xu

(Submitted on 9 Apr 2012)

Waveform-controlled Terahertz (THz) radiation is of great importance due to its potential application in THz sensing and coherent control of quantum systems. We demonstrated a novel scheme to generate waveform-controlled THz radiation from air plasma produced when carrier-envelope-phase (CEP) stabilized few-cycle laser pulses undergo filamentation in ambient air. We launched CEP-stabilized 10 fs-long (~ 1.7 optical cycles) laser pulses at 1.8 {\mu}m into air and found that the generated THz waveform can be controlled by varying the filament length and the CEP of driving laser pulses. Calculations using the photocurrent model and including the propagation effects well reproduce the experimental results, and the origins of various phase shifts in the filament are elucidated.

Comments:	5pages, 5 figures
Subjects:	Optics (physics.optics); Plasma Physics (physics.plasm-ph)
Cite as:	arXiv:1204.1860v1 [physics.optics]