Ultrafast modulation of ferroelectric polarization in a $\rm Ba_{0.8}\rm Sr_{0.2}\rm TiO_3$ film with an intensive subperiodic terahertz pulse

The results of an experimental and theoretical study of the effect of an intense, single-period terahertz pulse on the ferroelectric polarization in a barium–strontium titanate film are presented. Modulation of the ferroelectric polarization in the field of a terahertz pulse with a strength of up to $23.2$ MV/cm is demonstrated via generation of the second optical harmonic. The presence of a nonlinear dependence of the intensity of the second optical harmonic on the electric field strength of the THz pulse is shown.