Air-Plasma characterization at THz frequency range

Air-plasma is a common and convenient way to obtain intense and broad-band terahertz (THz) wave in laboratory. However, less attention has been paid on the plasma effect to the generated THz wave. To give a more comprehensive understanding, we characterize the transmitting property of air-plasma at THz frequency range. Resonant absorption of air-plasma is identified. The polarization dependence of the absorption is also studied. This work is not only a supplementary to the existing theory of THz generation, but also an alternative for plasma diagnostics.