Gas-pressure dependence of terahertz-pulse generation in a laser-generated nitrogen plasma

Far-infrared (terahertz) pulses can be generated by photoionization of electrically biased gases with amplified laser pulses [T. Loffler, F. Jacob, and H. G. Roskos, Appl. Phys. Lett. 77, 453 (2000)]. The efficiency of the generation process can be significantly increased when the absolute gas pressure is raised because it is then possible to apply higher bias fields close to the dielectric breakdown field of the gas which increases with the pressure. The dependence of the THz output on the optical pump power does not show any indication of saturation, making the plasma emitter an interesting source for THz pulses especially in conjunction with terawatt laser systems. (C) 2002 American Institute of Physics.