Excitation of coherent optical phonons in iron garnet by femtosecond laser pulses

TL;DR

This study investigates how femtosecond laser pulses can coherently excite optical phonons in iron garnet, confirming impulsive stimulated Raman scattering as the excitation mechanism through pump-probe experiments and symmetry analysis.

Contribution

It demonstrates the excitation of specific phonon modes in iron garnet using femtosecond pulses and confirms ISRS as the underlying process with experimental validation.

Findings

Coherent optical phonons are excited via ISRS.

Experimental results match spontaneous Raman spectra.

Selective excitation confirmed by polarization measurements.

Abstract

We employed femtosecond pump probe technique to investigate the dynamics of coherent optical phonons in iron garnet. A phenomenological symmetry-based consideration reveals that oscillations of the terahertz T2g mode are excited. Selective excitation by a linearly polarized pump and detection by a circularly polarized probe confirm that impulsive stimulated Raman scattering (ISRS) is the driving force for the coherent phonons. Experimental results obtained from ISRS measurements reveal excellent agreement with spontaneous Raman spectroscopy data, analyzed by considering the symmetry of the phonon modes and corresponding excitation and detection selection rules.