| Abstract: | The generation of terahertz(THz) emission from air plasma induced by two-color femtosecond laser pulses is studied on the basis of a transient photocurrent model.While the gas is ionized by the two-color femtosecond laser-pulses composed of the fundamental and its second harmonic,a non-vanishing directional photoelectron current emerges,radiating a THz electromagnetic pulse.The gas ionization processes at three different laser-pulse energies are simulated,and the corresponding THz waveforms and spectra are plotted.The results demonstrate that,by keeping the laser-pulse width and the relative phase between two pulses invariant when the laser energy is at a moderate value,the emitted THz fields are significantly enhanced with a near-linear dependence on the optical energy. |
