Generation of terahertz pulses by photoionization of electrically biased air

We present an experimental demonstration of the generation of far-infrared (terahertz) pulses by photoionization of electrically biased air with ampli fied laser pulses. The current surge following photoionization of the air w ith an applied bias field of 10.6 kV/cm leads to the emission of THz pulses with an intensity which can be almost as high as that of THz pulses radiat ed from a large-area intrinsic-field GaAs emitter. The spectra peak at high er frequency than those of biased large-area GaAs emitters. (C) 2000 Americ an Institute of Physics. [S0003-6951(00)01229-8].