title: Giant ultrafast photo-induced shear strain in ferroelectric BiFeO3.
abstract: Generation of strain using light is a key issue for future development of ultrasonic devices. Up to now, photo-induced GHz-THz acoustic phonons have been mainly explored in metals and semiconductors, and in artificial nanostructures to enhance their phononic emission. However, despite their inherent strong polarization (providing natural asymmetry) and superior piezoelectric properties, ferroelectric oxides have been only poorly regarded. Here, by using ultrafast optical pump-probe measurements, we show that photogeneration/photodetection of coherent phonons in BiFeO3 ferroelectric leads, at room temperature, to the largest intensity ratio ever reported of GHz transverse acoustic wave versus the longitudinal one. It is found that the major mechanism involved corresponds to screening of the internal electric fields by light-induced charges, which in turn induces stress by inverse piezoelectric effect. This giant opto-acoustic response opens new perspectives for the use of ferroelectric oxides in ultrahigh frequency acoustic devices and the development of new GHz-THz acoustic sources.
authors: Institut des Molécules et Matériaux du Mans, UMR CNRS 6283, Université du Maine, Av. O. Messiaen, 72085 Le Mans, France.
authors: Mariusz
authors: M
authors: Lejman
authors: Institut des Molécules et Matériaux du Mans, UMR CNRS 6283, Université du Maine, Av. O. Messiaen, 72085 Le Mans, France.
authors: Gwenaelle
authors: G
authors: Vaudel
authors: Laboratoire Structures, Propriétés et Modélisation des Solides, UMR CNRS 8580, Ecole Centrale Paris, 92295 Châtenay-Malabry, France.
authors: Ingrid C
authors: IC
authors: Infante
authors: Laboratoire Structures, Propriétés et Modélisation des Solides, UMR CNRS 8580, Ecole Centrale Paris, 92295 Châtenay-Malabry, France.
authors: Pascale
authors: P
authors: Gemeiner
authors: Laboratoire d'Acoustique de l'Université du Maine, UMR CNRS 6613, Université du Maine, 72085 Le Mans, France.
authors: Vitalyi E
authors: VE
authors: Gusev
authors: Laboratoire Structures, Propriétés et Modélisation des Solides, UMR CNRS 8580, Ecole Centrale Paris, 92295 Châtenay-Malabry, France.
authors: Brahim
authors: B
authors: Dkhil
authors: Institut des Molécules et Matériaux du Mans, UMR CNRS 6283, Université du Maine, Av. O. Messiaen, 72085 Le Mans, France.
authors: Pascal
authors: P
authors: Ruello