Abstract-Off-Axis Phase-Matched Terahertz Emission from Two-Color Laser-Induced Plasma Filaments

http://prl.aps.org/abstract/PRL/v109/i18/e183902

Y. S. You, T. I. Oh, and K. Y. Kim^* 
Institute for Research in Electronics and Applied Physics, University of Maryland, College Park, Maryland 20742, USA

Received 12 February 2012; published 31 October 2012

We observe off-axis phase-matched terahertz generation in long air-plasma filaments produced by femtosecond two-color laser focusing. Here, phase matching naturally occurs due to off-axis constructive interference between locally generated terahertz waves, and this determines the far-field terahertz radiation profiles and yields. For a filament longer than the characteristic two-color dephasing length, it emits conical terahertz radiation in the off-axis direction, peaked at 4–7° depending on the radiation frequencies. The total terahertz yield continuously increases with the filament length, well beyond the dephasing length. The phase-matching condition observed here provides a simple method for scalable terahertz generation in elongated plasmas.

© 2012 American Physical Society