Polarization switching in ferroelectric thin film induced by a single-period terahertz pulse

We report here an experimental study of ultrafast response of the dielectric polarization in (Ba 0.8 Sr 0.2 )TiO 3 thin films to a strong electric field of a nearly single-cycle THz pulse. The phenomenon of Second Harmonic Generation (SHG) is used as a probe of the polarization in the terahertz pump-optical probe experiment. SHG loops for THz pulses of different amplitudes were obtained. The SHG response is modelled assuming that the ferroelectric material is split into 180-degree domains. It is shown that intuitive model based on forced harmonic oscillator does not fully describe to the observed ultrafast ferroelectric response