The ultrafast switching of magnetization in multiferroic materials by a femtosecond laser could provide various advantages in photonics and magnonics. An efficient approach to control the lightmatter interaction is the modulation of ultrafast coherent magnons and phonons in the highfrequency range. Spontaneous Raman and infrared spectra reveal the excitation of magnons and optical phonons in multiferroic BiFeO3 in the sub-few-terahertz range. However, coherent control of such quasiparticles has not been achieved yet. In this study, we demonstrate that linearly polarized laser pulses simultaneously excite coherent magnons [out-of-plane (Ψ) and in-plane (Φ)cyclone modes] and optical phonon (E mode) in BiFeO3. Experimental results in conjugation with phenomenological theory, by considering three uniformly distributed magnetic domains, reveal that impulsive stimulated Raman scattering is responsible for the generation of coherent magnons and phonons in BiFeO3. The observation of these terahertz magnon and optical phonon modes paves the way for the development of ultrafast magnetoelectro-optical devices.

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.