CC BY
4The 30th International Conference on Advanced Laser Technologies
ALT'23
LM-I-3
Laser plasma source of powerful unipolar THz pulses
D.Gorlova, A. Savel'ev
Faculty of Physics, Lomonosov Moscow State University, 119991, Leninskie gory 1 bld.62, Moscow, Russia
gorlova. da14@physics. msu. ru
Generation of THz radiation in the interaction of laser pulse with intensity ~5-1018 W/cm2 with a controlled preplasma, created by an additional laser pulse interacting with a 16 p,m polymer film target, was studied. The mechanism of generation of THz radiation in the frequency range 1 -5 THz was found to be coherent transition radiation (CTR) of accelerated electrons traversing the rear plasma-vacuum boundary. The THz radiation yield is well correlated with the simultaneously measured relativistic electrons' yield (Fig.1). Integral THz radiation energy reaches ~0.1 mJ in the 1 -5 THz spectral range, corresponding to 0.2% laser-to-THz conversion efficiency, and increases linearly with laser pulse energy. Temporal envelope of the THz pulse was studied numerically using the CTR theory and experimentally with Michelson interferometric measurements, confirming close to unipolar pulse structure (Fig.2).
Fig.1. Dependences of the THz radiation energy and LANEX screen signal (-number of electrons with energy E>3 MeV) on the delay between the main pulse and the prepulse. The inset shows a typical electron beam spatial profile in the delay range from -4 to 0 ns.
Fig.2. Experimentally measured THz radiation power spectral density (a) and corresponding autocorrelation function (shown in the inset) for the delay -1 ns (a), numerically calculated THz pulse shape for delay -1 ns and different preplasma cloud characteristic sizes (shown in the graph, in mkm) (b) and autocorrelation function of (b) for 500 mkm preplasma size.
We also considered scaling of the proposed scheme toward multi TW and PW laser systems. Numerical simulations indicate maintained level of THz radiation efficiency for the optimized schemes and parameters.
[1] D. Gorlova, I. Tsymbalov, R. Volkov, and A. Savel'ev. Transition radiation in the thz range generated in the relativistic laser—tape target interaction. Laser Physics Letters, 19(7):075401(2022).
[2] Д. А. Горлова, И. Н. Цымбалов, К. А. Иванов, и А. Б. Савельев. Генерация терагерцевого излучения с экстремальными параметрами с использованием мультипетаваттного лазерного пучка. Квантовая электроника, 53(3):259-264 (2023).
