Far-infrared phonon-polariton dispersion probed by terahertz time-domain spectroscopy

Abstract

We report observations of the intensity and phase transmission spectra related to phonon-polariton propagation using coherent far-infrared radiation for a high-quality ferroelectric bismuth titanate crystal plate. In order to determine the polariton-dispersion relation, the phase delay was determined minutely as a function of the THz radiation frequency in the region between 3 and 100 (formula presented). The anisotropy of polariton dispersion relation was also successfully determined on the c plate simply by switching the polarization direction of an incident beam from (formula presented) to (formula presented) The observed polariton dispersion relations are consistently reproduced by the calculation using Kurosawa’s formula. © 2003 The American Physical Society.