Forward and backward terahertz emission by ionizing two-color laser pulses in gas is investigated by means of a simple semianalytical model based on Jefimenko’s equations and rigorous Maxwell simulations in one and two dimensions. We find the emission in the backward direction has a much smaller spectral bandwidth than in the forward direction and explain this by interference effects. Forward terahertz radiation is generated predominantly at the ionization front and is thus almost not affected by the opacity of the plasma, in excellent agreement with results obtained from a unidirectional pulse propagation model.
© 2011 Optical Society of America
Original Manuscript: May 17, 2011
Revised Manuscript: June 22, 2011
Manuscript Accepted: July 12, 2011
Published: August 11, 2011
C. Köhler, E. Cabrera-Granado, I. Babushkin, L. Bergé, J. Herrmann, and S. Skupin, "Directionality of terahertz emission from photoinduced gas plasmas," Opt. Lett. 36, 3166-3168 (2011)