Simulation of Laser Pulse Driven Terahertz Generation in Inhomogeneous Plasmas

Intense, short laser pulses propagating through plasma generate THz radiation. Full format PIC simulations and theoretical analysis are conducted to investigate two mechanisms of ponderomotively driven THz radiation: transition radiation, and slow wave phase matching enabled by corrugated plasma channels. The first mechanism occurs as a laser pulse crosses a plasma boundary [1] and is analogous to transition radiation emitted by charged particle beams. The THz radiation resulting from this transition radiation mechanism (TRM) is characterized by conical emission and a broad spectrum with the maximum frequency occurring near the plasma frequency. The second mechanism occurs in axially periodic plasma channels [2, 3]. These channels support electromagnetic modes with slow wave (Floquet-type) dispersion, which can be phase matched to the ponderomotive current. The slow wave phase-matched radiation (SWPM) is characterized by lateral emission and a coherent spectrum with sharp modes at frequencies associated with the channel. \\[4pt] [1] L. M. Gorbunov et. al., Plasmas Physics Reports Vol. 32, No. 10 (2006).\\[0pt] [2] T. M. Antonsen et. al., Phys. Plasmas 14, 033107 (2007).\\[0pt] [3] A. J. Pearson et. al., Phys. Review E 83, 056403 (2011).