TRANSIENT REVERSAL OF FERROELECTRIC POLARIZATION INDUCED BY TERAHERTZ ELECTROMAGNETIC PULSE

Abstract

The paper presents the results of an investigation of the ultrafast nonlinear-optical response of a thin film (Ba0.8Sr0.2)TiO3(001) to a terahertz frequency electromagnetic field pulse with duration near 1ps and electric field up to 500 kV/cm. Nonlinear optical response was a method to detect the ferroelectric polarization. The initial spontaneous polarization was perpendicular to the film, terahertz electric field was in-plane of the film. We demonstrated that ferroelectric polarization repeats the profile of the THz pulse during its impact and switches along the field direction. After the end of the THz pulse, the longlive (>20ps) oscillations were observed. The frequency of these oscillations correspond to the frequency of the soft mode in this material. Microscopic discription of nonlinear susceptibility explains the resonant behavior of nonlinear-optical response in THz range.

Keywords

• terahertz radiation
• ferroelectric
• polarization switching
• second harmonic generation