High-frequency shift and extension of the terahertz radiation spectrum up to 10 Thz during optical rectification of high-power few-cycle near-infrared femtosecond pump radiation in a BNA crystal

The generation of terahertz radiation in a BNA crystal pumped by 1.24-$\mu$m femtosecond laser radiation from a Cr:forsterite laser system with a pulse duration of 100 and 35 fs and a pump density of 10 mJ/cm$^2$ has been realized. The achieved generation efficiency is 0.1%. It is found that a decrease in the pump pulse duration from 100 to 35 fs leads to the generation of high-frequency components in the ranges of 2.5–6.5 THz and 9–10.5 THz in the generated radiation spectrum. Simulation of the terahertz radiation generation based on the solution of Maxwell's equations by the finite-difference time-domain method has made it possible to adequately describe the measured spectra. The generation of broadband high-frequency terahertz radiation in the BNA crystal pumped by the Cr:forsterite laser system allows one to consider this schematic as an alternative to sources based on the BNA crystal pumped by a Ti:sapphire laser system.