Terahertz radiation induced by coherent phonon generation via impulsive stimulated Raman scattering in paratellurite

TL;DR

This study demonstrates terahertz radiation generation in paratellurite via coherent phonons excited by impulsive stimulated Raman scattering, revealing interference patterns and phonon-related oscillations at room temperature.

Contribution

It provides the first detailed observation and explanation of terahertz radiation induced by coherent phonons in paratellurite, highlighting the role of impulsive stimulated Raman scattering.

Findings

Observation of terahertz radiation with fringe patterns below 3 THz.

Detection of a 3.71 THz oscillation matching Raman-active phonon mode.

Explanation of the generation mechanism via coherent phonon excitation.

Abstract

We report on the observation of terahertz radiation in a non-centrosymmetric insulating oxide, paratellurite ($\alpha$-TeO$_2$) by irradiation of a femtosecond laser pulse at room temperature. In the power spectrum of the terahertz radiation, an intensity fringe pattern with a period of $\sim$ 0.25 THz shows up below 3 THz. It can be reproduced by taking into account the effective generation length for the terahertz radiation with a poor phase-matching condition. In addition, a temporal oscillation component appears in the radiated terahertz wave with a frequency of $\sim$ 3.71 THz, which is in good agreement with the center frequency of the Raman active longitudinal optical (LO) $E$ mode. On the basis of comprehensive polarized optical and Raman spectroscopic studies, we explain the generation mechanism of the temporal oscillation component in terms of the coherent phonon generation via impulsive stimulated Raman scattering.