Role of polarization-photon coupling in ultrafast terahertz excitation of ferroelectrics

We investigate the role of polarization-photon coupling (specifically, polarization-oscillation-induced radiation electric field) in excitation ferroelectric thin films by an ultrafast terahertz field pulse. Analytical formulas are developed to predict how frequencies and relaxation time three-dimensional soft mode phonons (intrinsic polarization oscillation) modulated epitaxial strain. Ultrafast terahertz-pulse-driven harmonic oscillation strained single-domain film is then simulated using a dynamical phase-field model that considers coupled strain-polarization-photon dynamics. The extracted from such numerical simulations agree well with analytical predictions. In relatively films, it predicted slightly reduces but significantly shortens time. These results demonstrate necessity considering understanding predicting response materials pulses higher frequencies.