Frequency spectrum characterization of terahertz emission from l...

Terahertz (THz) emission from laser-induced air-plasma is presented. The frequency spectra of THz wave are investigated using an air-biased-coherent-detection method. The frequency spectra are measured under different pump-pulse and probe-pulse energies. The frequency spectra become narrow with the increasing pump power and we speculate it caused by collision behavior. Meanwhile, the bandwidth of the frequency spectra is broadened by the increasing probe power, which can be explained by pulse co