Electrically tuned transmission and dielectric properties of illuminated and non-illuminated barium titanate thin film in terahertz regime

Transmission and dielectric properties of non-illuminated and illuminated barium titanate thin film were investigated by time-domain terahertz spectrometer and tuned by an electric field. Compared with the sample illuminated by 532 nm laser, the electric field could realize a higher modulation in the phase of the transmission for the nonilluminated sample. Results displayed that when the sample was illuminated by green laser, optical field suppressed the effect of electric field on transmission and dielectric properties of BTO thin film, because excited carriers from the substrate and ferroelectric thin film would form a built-in electric field to shield the external electric field. In addition, optical field and electrical field would play different roles in the lattice dynamics of the ferroelectric thin film.