Ultrafast photostriction in ferroic compounds.*

Ferroic compounds have intrinsically a large electro-mechanical coupling playing a central role in many devices in telecommunications and sensors technologies. To push the devices in the GHz-THz regime, only a control of the ferroic properties with light is possible. Among perspectives, the control of motion and strain with ultrafast light pulse should open new perspectives for light-controlled devices (actuators, mechatronics). To reach this goal, it is crucial to understand how the light energy is converted into mechanical energy (acoustic phonons) in these ferroic compounds. We then have studied the ultrafast generation/detection of coherent acoustic phonons in ferroics compounds within the pump-probe scheme. We show that ferroelectric BiFeO₃ offers unique properties to emit/detect coherent transverse (TA) and longitudinal (LA) acoustic phonons [1]. This phenomenon is attributed to an ultrafast screening of the ferroelectric polarization. Beside a rich electron-phonon coupling physics [1-3], we also evidence original ultrafast acousto-optic processes (i.e. a conversion of the probe light polarization from ordinary to extraordinary (and vice-versa) recently revealed in ferroelectrics such as LiNbO₃ and BiFeO₃ [4]. By demonstrating the manipulation of light polarization with 10-100 GHz coherent acoustic phonons, our results highlight new capabilities in using ferroelectrics in modern photoacoustics and photonics.
[1] Lejman M., Vaudel G., Infante, I. C., Gemeiner P., Gusev V., Dkhil B., Ruello P., Nature Comm. 5, 4301 (2014).
[2] Schick, D. et al., Phys. Rev. Lett. 110, 095502 (2013).
[3] H. J. Lee et al, Scientific Reports, 6, 38724 (2016)
[4] Lejman M., Vaudel G., Infante I-C., Chaban I., Pezeril T., Edely M., Nataf G., Guennou M., Kreisel J., Gusev V. E., Dkhil B., Ruello P., Nature Comm. 7, 12345 (2016).