CC BY
15THz-I-7
Methods of intense THz generation by multiterawatt,
800 nm laser pulses
M. M. Nazarov1' P. A. Shcheglov1, M. V. Chaschin1, A.V.Mitrofanov1'3'4, D. A. Sidorov-Biryukov1'2'3, A.A. Voronin2, A. M. Zheltikov1'2'3'5 and V. Ya. Panchenko1'2'4
1 Kurchatov Institute National Research Center, Moscow 123182, Russia 2 Physics Department, M.V. Lomonosov Moscow State University, Moscow 119992, Russia 3 Russian Quantum Center, Skolkovo, Moscow Region 143025, Russia 4 Inst. Laser and Information Technol. - Branch of FSRC "Cryst. and Photonics," RAS,
Shatura, 140700 Russia
5 Department of Physics and Astronomy, Texas A&M University, College Station TX 77843, USA
High-power terahertz (THz) sources [1-3] are in great demand as tools for the single-shot spectroscopy, advanced imaging, time-resolved studies. All these rapidly growing areas of research call for powerful and broadband, yet compact and robust sources of THz pulses. Leading this quest is the optical rectification (OR) of ultrashort laser pulses in quadratically nonlinear materials. For pumpprobe experiments in strong fields with 30 fs temporal resolution, a simple method is required to obtain strong THz pulses from 0.8 ^m multiTW laser systems. We demonstrated that the well-developed lithium niobate (LN) wafers have advantages in this situation, despite strong THz absorption and the absence of phase matching
THz generation in large-area LN wafers has been shown [1] to enable an OR of ~2-J, 25-fs laser pulses to 0.19-mJ THz waveforms with the coherence length for OR, lc«50 ^m, is much shorter than the thickness of an LN wafer. Here, we aim at identifying the physical factors that limit the terahertz yield of an OR of ultrashort multiterawatt laser pulses in large-area thin LNs. We show that the THz yield tends to slow its growth as a function of the laser driver energy, saturate, and eventually decrease as the laser beam picks up a spatiotemporal phase due to the intensity-dependent refraction of the OR crystal. Non-phasematched generation in a thin layer provides significantly broadband and short THz pulses in comparison with other studied methods: two-color gas breakdown [3] and metal foil ablation at subrelativistic intensities [4]. As a result, in LN with 250 mJ of laser energy, we obtained a 10 J single-cycle THz pulse with a broad, smooth spectrum, containing 40% of the energy at frequencies above 3 THz. That is twice more energetic THz pulse than obtained in a rare gas plasma pumped with the same laser system. This work was partially supported by RFBR grants 18-52-16024, and 18-0240032
REFERENCES:
[1] D. Jang, C. Kang, S.K. Lee, et.al. Optics Letters, 44, 5634-5637, (2019)
[2] M. Jazbinsek, U. Puc, A. Abina, A. Zidansek, Appl. Sci., 9, 882 (2019)
[3] M. M. Nazarov, A. V. Mitrofanov, D. A. Sidorov-Biryukov, et.al. JIMTW, 1-13.(2020).
[4] M. M. Nazarov, P. A.Shcheglov, M. V.Chaschin, et.al. JPCS, 1692, 012018, (2020).
