CC BY
10Efficient strong-field THz generation from organic crystal BNA
pumped by 1030 nm Yb-laser
K. Brekhov1'2*. S. Kolar3, E. Chiglintsev2 3, A. Chernov23
1-MIREA - Russian Technological University, Vernadsky Avenue 78, Moscow, 119454, Russia 2- Russian Quantum Center, Skolkovo Innovation City, Moscow, 121205, Russia 3- Moscow Institute of Physics and Technology, Institutskiy Pereulok 9, Dolgoprudny, Moscow Oblast, 141701,
Russia
With successive development, terahertz (THz) radiation can be achieved in various materials, such as solid, gas, liquid, and plasma, pumped by ultrafast laser pulses. THz radiation is used both for THz spectroscopy and for studying the dynamics of various processes that arise in a medium under the influence of THz pulses.
To date, the common methods of THz generation are based on photoconductive antennas, spintronic emitters and nonlinear crystals. To study THz-induced dynamics in various materials, sources of high THz fields are needed. Currently, for this are used, for example, semiconductors such as gallium phosphide and zinc telluride and ferroelectric crystal such as lithium niobate. However, they have low conversion of optical to THz radiation. The greatest efficiency of such conversion is demonstrated by organic crystals such as OH1, DSTMS, DAST and BNA. Since compared to inorganic crystals, organic crystals have a much higher second-order nonlinear optical susceptibility, which benefits THz generation via optical rectification (OR).
However, to fulfill the phase matching condition for THz generation, most organic crystals need to be excited by infrared laser centered at 1300-1700 nm, provided by optical parametric amplifiers (OPA). This is unfortunate because present high energy near infrared pump lasers operate below 1.3 ^m, such as Cr:forsterite (1.24 ^m), Yb-lasers (1.05 ^m ) and Ti:Sap-lasers (0.8 ^m) [1]. Infrared OPA sources have been employed to pump DSTMS and DAST crystals and Cr:forsterite lasers have been employed to pump OH1 crystal for strong-field THz generation. But such systems are normally high-cost and complex to operate. Ti:Sap lasers have also been used to pump BNA organic crystals for THz generation, but with relatively low energy conversion efficiency.
Therefore, an economical, miniaturized, high-power ytterbium Yb-doped laser has attracted the researcher's attention. It is typically sub-picosecond in pulse duration and up to several millijoules in pulse energy with a high level of technological maturity and has been commercially available in scientific research and industry. Nevertheless, there is still a lack of reports on strong-field THz generation based on Yb-laser. There are two reasons for this. One is that the picosecond pulse duration of the Yb-laser is too long for effective OR process; and the second is that the thermal properties were believed to be a limiting factor for high average power excitation.
Here we present BNA organic crystal as a candidate for efficient THz generation from near infrared laser systems. We report collinear strong-field THz generation from the BNA organic crystal on a sapphire substrate for heat dissipation, driven by an industrial-grade Yb-laser operating at 1030 nm. The laser pulse duration was compressed up to 20-100 fs by using Compulse - Hollow Fiber Pulse Compressor and chirped mirrors. The dependence of the emission spectrum on the pump pulse duration was estimated. The output THz energy reaches 0.45 J with a conversion efficiency of 0.37%. The peak electric field was about 440 kV/cm. So, we demonstrate that a 1030 nm Yb-laser is used to pump BNA organic crystal for efficient THz generation in a simple collinear geometry, which provides a promising THz source based on an industrial-grade ultrafast laser.
This work was supported by the Russian Science Foundation, grant № 22-12-00334.
[1] K. Wang, Z. Zheng, H. Li, et al, Efficient strong-field THz generation from DSTMS crystal pumped by 1030nm Yb-laser, Appl. Phys. Lett. 124, 121102 (2024).
[2] H. Zhao, Y. Tan, T. Wu, et al, Efficient broadband terahertz generation from organic crystal BNA using near infrared pump, Appl. Phys.
Lett. 114, 241101 (2019).
