||Terahertz time-domain spectroscopy of Raman inactive phonon-polariton in strontium titanate
Kojima, SeijiMori, Tatsuya
106 , 2016-05 , Taylor & Francis
The Raman inactive low-frequency phonon-polariton was studied in a quantum paraelectric strontium titanate crystal. The lowest frequency IR active T1u mode was investigated by the reflectance and transmittance Terahertz Time-Domain Spectroscopy using the pulse coherent THz radiation from 0.2 to 5.0 THz. The complex dispersion relations were determined using the real and imaginary parts of a polariton wavevector calculated from the complex refractive index which reflects the T1u symmetry phonon-polariton. The remarkable change of the dispersion relation was observed in the vicinity of TO and LO mode frequencies for both real and imaginary parts of a polariton wave vector. The observed complex dispersion relation of T1u symmetry is in agreement within the experimental uncertainty with the dispersion curves fitted by the damped harmonic oscillator model.