Investigation of Polarization Effect on Terahertz-Enhanced Air Plasma Acoustic Emission

Abstract

Terahertz (THz)-enhanced air plasma acoustic emission has been used to investigate plasma dynamics and detect THz pulses. Here, we report the laser polarization dependence of air plasma acoustic wave under THz field illumination. The angular distribution of plasma acoustic emission is systematically characterized. The THz-enhanced acoustic efficiency for laser pulse with circular polarization is obviously higher than that with linear polarization, although the acoustic pressure induced by circularly polarized laser pulse is smaller. We attribute this effect to THz-driven electron acceleration and subsequent electron–molecule collision, while the electron densities and THz wave absorptions in plasma are significantly distinct for different laser polarizations due to multiphoton ionization in air. Our findings provide useful information for THz–plasma interaction and hold potential to further strengthen the THz detection capability through “listening” to the plasma.