Thursday, April 23, 2015

Abstract-Strong terahertz emission from electromagnetic diffusion near cutoff in plasma

M-H Cho1,5, Y-K Kim2, H Suk3,7, B Ersfeld4, D A Jaroszynski4,7 and M S Hur1,6
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1 School of Natural Science, UNIST, Ulsan, 689-798, Korea
2 School of Electrical and Computer Engineering, UNIST, Ulsan, 689-798, Korea
3 Department of Physics and Photon Science, GIST, Gwangju, 500-712, Korea
4 Department of Physics, Scottish Universities Physics Alliance and University of Strathclyde, Glasgow G4 0NG, UK
5 Center for Relativistic Laser Science, Institute for Basic Science (IBS), Gwangju 500-712, Korea
6 Author to whom any correspondence should be addressed.
7 Co-corresponding authors. 

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 MV m−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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