Terahertz wave emission from laser-induced micro-plasma

Laser-induced plasmas with longitudinal size smaller than 40 μm are investigated as a source of broadband terahertz (THz) radiation. The angular dependent emission of the micro-plasma is measured with coherent detection, and the preferential directions of radiation are identified. The observations support electrons drift driven by the laser ponderomotive force as the principal generation mechanism. We also report the measurement of THz waveforms with pump pulse energies as low as 0.66 μJ. The experimental results suggest the laser-induced micro-plasma as a promising approach to scale down the power budget for broadband terahertz spectroscopy.