Zharova N A, Mironov V A, Fadeev D A
Institute of Applied Physics, Russian Academy of Sciences, 46 Ulianov Street, Nizhny Novgorod 603950, Russia.
Phys Rev E Stat Nonlin Soft Matter Phys. 2010 Nov;82(5 Pt 2):056409. doi: 10.1103/PhysRevE.82.056409. Epub 2010 Nov 18.
Strong terahertz (THz) radiation can be generated by intense femtosecond laser pulses propagating in air. The excitation of transient current induced in the wake just behind the laser pulse is studied in detail using numerical simulations on the basis of Maxwell's equations for THz-band fields and hydrodynamic model for the plasma motion. It is shown that the thermal effects, anisotropic in character in the case of linear polarized laser field, can explain observed quadrupole-type THz radiation pattern in the experiment performed by Akhmedzhanov [Radiophys. Quantum Electron. 52, 482 (2009)]. Taking into account the transverse structure of the plasma filament, our numerical code enables us to calculate the spatial distribution and temporal evolution of terahertz electron current, its spectrum, and angular emission pattern. It is shown that an expansion of full fields in terms of azimuthal modes is a useful tool for research of THz generation in many situations of practical interest.
强太赫兹（THz）辐射可由在空气中传播的强飞秒激光脉冲产生。基于太赫兹波段场的麦克斯韦方程组和等离子体运动的流体动力学模型，通过数值模拟详细研究了激光脉冲后方尾流中感应的瞬态电流的激发情况。结果表明，在线偏振激光场情况下具有各向异性的热效应，可以解释Akhmedzhanov [《无线电物理与量子电子学》52, 482 (2009)] 所做实验中观测到的四极型太赫兹辐射图样。考虑到等离子体细丝的横向结构，我们的数值代码能够计算太赫兹电子电流的空间分布和时间演化、其频谱以及角发射图样。结果表明，在许多实际感兴趣的情况下，用方位角模式展开全场是研究太赫兹产生的一种有用工具。
