Abstract-Narrowband terahertz radiation by impulsive stimulated Raman scattering in an above-room-temperature organic ferroelectric benzimidazole
M. Sotome, N. Kida, S. Horiuchi, and H. Okamoto
In noncentrosymmetric media, optical rectification is known to be a general mechanism of the generation of terahertz electromagnetic waves. Here, we show that effective terahertz radiation is possible via a different mechanism in a hydrogen-bonded organic molecular ferroelectric 5,6-dichloro-2-methylbenzimidazole (DCMBI). By the irradiation of a femtosecond laser pulse on a single crystal of DCMBI at room temperature, we observe a strong terahertz radiation. 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 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. {I.
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