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Graduate Student Seminar - 11/21/2014

"Simulation of Laser Pulse Driven Terahertz Generation in Inhomogeneous Plasmas"

by Chenlong Miao

Friday, November 21, 2014 -- 12:00 p.m.
Large Conference Room, 1207 Energy Research Facility

Advisor:  Professor Thomas Antonsen

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: (i) transition and (ii) slow wave phase matching enabled by corrugated plasma channels. The first mechanism occurs as a laser pulse crosses a plasma boundary 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. 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. As an example, a fixed driver pulse (1.66 J) with 15 micron spot size in a short 500-micrometer-long modulated channel with on-axis average density of 1.4 x 1018cm-3, the THz radiation is approximately 33.6 μJ and 83.7 μJ from TRM and SWPM, respectively.

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