Broadband and narrowband laser-based terahertz source and its application for resonant and non-resonant excitation of antiferromagnetic modes in NiO.

A versatile table-top high-intense source of terahertz radiation, enabling to generate pulses of both broadband and narrowband spectra with a tunable frequency up to 3 THz is presented. The terahertz radiation pulses are generated by optical rectification of femtosecond pulses of Cr:forsterite laser setup in nonlinear organic crystal OH1. Electric field strengths of broadband and narrowband terahertz pulses were achieved close to 20 MV/cm and more than 2 MV/cm, correspondingly. Experiments on excitation of spin subsystem oscillations of an antiferromagnetic NiO were carried out. Selective excitation of 0.42 THz mode was observed for the first time at room temperature by a narrowband terahertz pulses tuned close to mode frequency.