Abstract

The polariton dispersion relation is the very important basic properties for such an application of the frequency-tunable terahertz laser radiation. Nevertheless, the study of the dispersion relation including the damping of polariton has been quite few. Up to the present the polariton dispersion relation was mainly studied by Raman scattering in the forward scattering geometry. However, there are two serious disadvantages. At first the uncertainty of wave vector of scattering light at small angle scattering causes the difficulty for the determination of a damping factor of polariton. Secondly, it is impossible to study Raman inactive polariton in centrosymmetric crystals. Therefore, terahertz time-domain spectroscopy (THz-TDS) is a powerful tool to study phonon-polariton dispersion relation.^1,2

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