Simulation study of plasma dipole oscillation applying field ionization effect

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

Radiation sources in the terahertz (THz) spectral band have been studied for use in a variety of application. Free-electron-lasers (FELs) have been developed that typically produce powerful THz radiation source in broadband [1]. Plasma dipole oscillation (PDO) can overcome some of the disadvantages of these radiation sources (e.g., huge devices and expensive cost). PDO is a new THz radiation source that emits at plasma frequency (ωp∝√n) (where n is the local electron density) in a narrowband [2]. When two lasers collide inside plasma, the electrons are pulled by the beat wave generated by ponderomotive (PM) potential. As a results, the moving trapped electrons oscillate by electrostatic restoring force. In this study, we present PDO to which field ionization Ammosov-Delon-Krainov (ADK) model [3] is applied. Generally, PDO is produced by a laser detuned in a plasma strip. However, in the case of He gas when a high-intensity laser is launched, a plasma strip is created by the field ionization effect, and the local electron density is doubled, increasing the plasma frequency. This means that the PDO’s THz radiation band will be higher. Also, it was confirmed through simulation that the y-direction PM force affects the PDO generation when the laser collides at an oblique angle.

[1] Socol, Yehoshua. "High-power free-electron lasers–technology and future applications." Optics & Laser Technology 46 (2013): 111-126.

[2] 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.

[3] Ammosov, Maxim V., Nikolai B. Delone, and Vladimir P. Krainov. "Tunnel ionization of complex atoms and atomic ions in electromagnetic field." High intensity laser processes. Vol. 664. SPIE, 1986.