Response of LiTaO3 thin film to X-band short microwave pulse

Abstract

The response of the LiTaO3 thin film detector to the X-band pulse with large power (of order 10 W/cm2) and short duration (of order 0.1 μs) is investigated experimentally and explained from the viewpoint of dielectric relaxation. With the output voltage signal of the detector, the current through the LiTaO3 thin film and its electric polarization are computed and used to examine the observation in a more fundamental manner. In contrast to the common step excitation, the short pulse can provide a delta-type excitation and the response is more appropriate for exploring the interaction mechanism. It is demonstrated from the viewpoint of energy that the response of the detector is not caused by the temperature change in the film, which is the core component in the traditional model of the pyroelectric detector. The polarizations under different pulse conditions show that the interaction is nonlinear, so the linear superposition assumption in the dielectric relaxation theory cannot be used any more. It is found that the polarization can be fitted quite well with a sine function and a time-dependent frequency can be defined. An empirical equation is derived for the dynamics of polarization, and the accelerating and damping effects in the relaxation process can be explained with the relative change in this frequency. The dynamics analysis indicates that the electromagnetic energy is mainly dissipated through driving the domain wall in the crystal.