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

Abstract

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.

Highly Nonlinear Optical Organic Crystals for Efficient Terahertz Wave Generation, Detection, and Applications

“…The chirp-and-delay approach has already been successfully applied to several benchmark organic crystals, such as HMQ-TMS, DSTMS, and OH1, [43,47,[131][132][133] and the results demonstrate that a large tuning range of the generated THz pulses up to 7 THz (refer to Figure 11 [131] ), narrow bandwidth below 0.1 THz, and high field strength of several megavolts per centimeter can be achieved using this approach (also refer to an overview provided [132] ). Therefore, the advantage of using organic NLO crystals for multicycle narrowband THz pulse generation is similar to that for other schemes used for THz wave generation, i.e., the methods can achieve high THz pulse energies and a very broad tuning range of the central frequency.…”

Ultrafast manipulation of the NiO antiferromagnetic order via sub-gap optical excitation

“…This frequency is close to the eigenfrequency of the out-of-plane magnon mode, which has been extensively studied in both optical and THz Please do not adjust margins Please do not adjust margins spectroscopy measurements. 14,19,[41][42][43][44][45][46][47][48][49] There are two magnon eigenmodes: in-plane and out-of-plane modes. For the in-plane mode, the AFM vector between two adjacent ferromagnetic planes is modulated along the [1-10] direction, which lies in the (111) plane.…”

Narrow-band and tunable intense terahertz pulses for mode-selective coherent phonon excitation

“…The scheme we present has numerous advantages such as high fields and, moreover, fills the spectral gap of the existing laser-based narrow-band THz sources, such as the difference-frequency generation (DFG) in organic crystals, 11 which is suitable for higher frequencies (4-18 THz), or optical rectification by temporal modulated pulses in LiNbO 3 12,13 and HMQ-TMS, 14 which can cover lower frequencies of 0.3-1.3 THz and 0.3-0.8 THz, respectively. Our source is tunable over a spectral range, 0.5-6.5 THz, comparable with the one demonstrated using 10 Hz Cr:forsterite to pump an organic crystal, 15,16 but relies on a more commercially available optical-parametric amplifier (OPA) pump, which has the advantages of a higher repetition rate and a tunable wavelength for optimal pumping of different organic crystals. The higher repetition rate achievable with an OPA and the high field demonstrated here turn into a higher signal-to-noise ratio, which is crucial for future spectroscopic applications.…”