Temporal and spatial tracking of ultrafast light-induced strain and polarization modulation in a ferroelectric thin film

Abstract

Ultrashort light pulses induce rapid deformations of crystalline lattices. In ferroelectrics, lattice deformations couple directly to the polarization, which opens the perspective to modulate the electric polarization on an ultrafast time scale. Here, we report on the temporal and spatial tracking of strain and polar modulation in a single-domain BiFeO 3 thin film by ultrashort light pulses. To map the light-induced deformation of the BiFeO 3 unit cell, we perform time-resolved optical reflectivity and time-resolved x-ray diffraction. We show that an optical femtosecond laser pulse generates not only longitudinal but also shear strains. The longitudinal strain peaks at a large amplitude of 0.6%. The access of both the longitudinal and shear strains enables to quantitatively reconstruct the ultrafast deformation of the unit cell and to infer the corresponding reorientation of the ferroelectric polarization direction in space and time. Our findings open new perspectives for ultrafast manipulation of strain-coupled ferroic orders.

Intermediate multidomain state in single-crystalline Mn-doped BiFeO3 thin films during ferroelectric polarization switching

“…The photovoltaic effect in ferroelectrics with a noncentrosymmetric crystal structure has been well investigated as a bulk photovoltaic effect (BPVE) that induces optical strains 11 – 15 by coupling with a converse piezoelectric effect. More recently, ultra-fast optical-induced strains and polarization modulations in (110)-oriented BiFeO 3 single-domain film by femto-second laser irradiation 16 . Thus, the characteristics and lattice distortions of ferroelectric semiconductors are deeply coupled via spontaneous polarization ( P s ), indicating that ferroelastic lattice distortion with P s vector rotation causes drastic modulation of the characteristics of ferroelectric semiconductors.…”