Strong terahertz emission from electromagnetic diffusion near cutoff in plasma

Cho, M-H and Kim, Y-K and Suk, H and Ersfeld, B and Jaroszynski, D A and Hur, M S (2015) Strong terahertz emission from electromagnetic diffusion near cutoff in plasma. New Journal of Physics, 17 (4). 043045. ISSN 1367-2630 (https://doi.org/10.1088/1367-2630/17/4/043045)

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Abstract

A new mechanism for electromagnetic emission in the terahertz (THz) frequency regime from laser-plasma interactions is described. A localized and long-lasting transverse current is produced by two counter-propagating short laser pulses in weakly magnetized plasma.We show that the electromagnetic wave radiating from this current source, even though its frequency is close to cut-off of the ambient plasma, grows and diffuses towards the plasma-vacuum boundary, emitting a strong monochromatic THz wave. With driving laser pulses of moderate power, the THz wave has a field strength of tens of MVm−1, a frequency of a few THz and a quasi-continuous power that exceeds all previous monochromatic THz sources. The novelty of the mechanism lies in a diffusing electromagnetic wave close to cut-off, which is modelled by a continuously driven complex diffusion equation.

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