Enhancing Conversion Efficiency of Plasma Dipole Oscillators for THz-based Linear Accelerators

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

Recently, terahertz (THz) light sources based on laser plasma have been studied for various applications such as THz-driven acceleration [3] and pump-probe experiments. Traditional solid-state THz sources often exhibit weakness in terms of causing material damage, which can be mitigated by utilizing THz sources in pre-ionized plasmas. However, they still have not achieved high conversion efficiency (< 0.5%) from laser to THz pulse energy. Here, we propose a novel scheme of THz sources based on laser plasma, known as “Plasma Dipole Oscillation” (PDO) (Fig. 1) [1–2]. This phenomenon is generated by two counterpropagating pulses with slightly different frequencies and can emit coherent THz radiation with a narrow bandwidth at the plasma frequency. In this presentation, we present a numerical study of high-efficiency PDO for THz-driven acceleration. Our previous research has already suggested a force-balanced model for PDO [1], and based on this, it has been confirmed through two-dimensional PIC (particle-in-cell) simulations that significantly higher efficiency (up to ~ 0.26%) can be obtained with optimal parameters (, τ, σ, θ, etc.) when the pulse shape is changed. Lastly, we propose a scheme for utilizing THz-driven accelerators [3] using high-efficiency PDO.

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

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

[3] Nanni, Emilio A, et al. "Terahertz-driven linear electron acceleration." Nat. Commun. 6, 8486 (2015).