Configuration of plasma dipole using two oblique colliding laser pulses in Helium gas

 J. Lee, H. S. Song, D. Park, M. Kumar and M. S. Hur

Previously we have proposed the novel of THz emission mechanism [1], named plasma dipole oscillation (PDO). Generally, it is produced that moving potential due to detuning of two laser pulse. Thus, trapped electrons in beat wave are coherently moved by electrostatic restoring force. PDO can emit electromagnetic (EM) radiation at the plasma frequency () of narrowband where n is the local plasma density. if we can control the local plasma density, we can obtain the desired narrow-band radiation i.e., few THz radiation. Originally, PDO have been proposed to compose in pre-loaded plasma strip [1]. However, this configuration is not friendly in experimental environment. Therefore, we suggested a method that can simply drive a PDO without the need to artificially create a plasma strip i.e., field ionization. It is readily to create a PDO when an intense laser pulse passes through neutral helium gas because a helium plasma strip naturally forms in the laser’s path. Also, it focuses on oblique angle for colliding two laser pulses. Which is strongly realistic configuration of PDO. In this study, we have performed two-dimensional (2D) particle-in-cell (PIC) simulation. When two laser pulses collide at oblique angle, we investigated that radiation emits in PDO and high order of dipole field (~ GV/m), total radiation energy (~mJ/mm). it is powerful evidence that PDO sustain in currently configuration.

[1] Kwon, Kyu Been, et al. "High-energy, short-duration bursts of coherent terahertz radiation from an embedded plasma dipole." Scientific reports 8.1 (2018): 1-9.