Observation of photoassisted polarization switching in BiFeO3 thin films probed by terahertz radiation

The authors have examined the effect of photoexcitation in a multiferroic BiFeO3 thin film using terahertz radiation as the probe. The illumination of femtosecond laser pulses with a center wavelength of 400 nm gave rise to a significant improvement in the polarization switching process by the application of bias electric field. This effect is attributed to the depinning of domain walls induced by carrier excitation as reported in ordinary ferroelectrics. The authors revealed that a significantly weak laser power in the order of submilliwatt is sufficient to invoke this effect.