Characteristic Study of Plasma dipole using two obliquely pulses in Helium gas

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

In the past, we proposed a new THz emission process called plasma dipole oscillation (PDO) [1]. PDO can be generated by beat frequency () of two colliding laser pulses. In this mechanism, electrons trapped in the ponderomotive potential (wave) of the laser pulses are displaced and oscillated by electrostatic force. PDO is capable of produces electromagnetic (EM) radiation with a narrow bandwidth at the plasma frequency (, where n is the local plasma density) and by adjusting the local plasma density, we can obtain narrowband radiation at the desired frequency. In our previous study, the PDO was produced in pre-loaded plasma strip [1]. However, this setup is not readily realized experimentally. Here we have studied a way that can produce a PDO by field ionization in neutral helium gas, without creating a pre-plasma strip. In conclusion, to verify PDO setup with neutral He gas, we have performed two-dimensional (2D) particle-in-cell (PIC) simulations. We observed radiation of PDO, which obtained a high dipole field (~ GV/m) and the total radiation energy was achieved of order ~ 0.1 mJ/mm.

[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.