Narrowband terahertz radiation by an impulsive stimulated Raman scattering in an above-room-temperature organic ferroelectric benzimidazole

TL;DR

This study demonstrates room-temperature terahertz radiation from an organic ferroelectric induced by femtosecond laser pulses, revealing a new method for light-induced terahertz generation in organic materials.

Contribution

It introduces a novel mechanism of terahertz radiation via impulsive stimulated Raman scattering in an above-room-temperature organic ferroelectric.

Findings

Terahertz emission matches Raman and infrared phonon modes.

Reproduced terahertz spectrum and time characteristics through analysis.

Identified impulsive stimulated Raman scattering as the radiation source.

Abstract

We observe a terahertz radiation from a hydrogen-bonded organic molecular ferroelectric 5,6-dichloro-2-methylbenzimidazole excited by a femtosecond laser pulse at room temperature. The emitted terahertz wave consists of three oscillatory components, the frequencies of which agree with those of Raman- and infrared-active phonon modes. This suggests that the terahertz radiation is attributed to polarization modulations by infrared-active phonons excited via the impulsive stimulated Raman scattering processes. By taking into account the Raman polarizability tensor and dipole-moment for each phonon, we succeeded in reproducing not only the spectrum of the terahertz radiation, but also its time characteristic. The analysis method is discussed in detail. Our result provides a new way for the light-induced terahertz radiation in organic ferroelectrics.