Theoretical formulation based on numerical PIC simulations for high-efficiency and multi-plasma oscillators

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

Recently, we discovered a new terahertz (THz) emission source termed “Plasma Dipole Oscillation” (PDO) [1,2]. This phenomenon arises when two counterpropagating laser pulses with slightly different detuning frequencies () interact within plasma. Following the collision of the laser pulses, plasma electrons are trapped in the beat wave due to the ponderomotive force. These trapped electron bunches are later released, resulting in THz pulse with a narrowband spectrum. Interestingly, PDOs not only function as a light source but also have the potential to display other nonlinear oscillation mechanisms. In recent two-dimensional (2D) particle-in-cell (PIC) simulations, we observed that when two identical PDOs are generated using four laser pulses, oscillator coupling occurs between the PDOs due to density perturbations along the transverse direction. Moreover, we found that this phenomenon closely resembles the behavior predicted by the coupled oscillator model in classical mechanics. In this presentation, we will discuss our latest discoveries regarding double-PDO coupling in plasmas and propose a new theoretical model for Langmuir wave coupling associated with type III solar radio bursts. 

[1] K. B. Kwon, et al. "High-energy, short-duration bursts of coherent terahertz radiation from an embedded plasma dipole." Sci. Rep. 8, 145 (2018). 

[2] J. Lee, et al. "Intense narrowband terahertz pulses produced by obliquely colliding laser pulses in helium gas." Phys. Plasmas 30, 4 (2023).