The THz spectra and analysis of Bi 4 Ge 3 O 12 crystal

THz time domain spectra of Bi 4 Ge 3 O 12 (BGO) crystal were measured. The refractive index and power absorption function and optical dielectric function were obtained. The time domain spectrum shows resonance characteristic. There was one strong absorption band in the range of 1.5–2.3 THz. And the refractive index exist abnormal dispersion in the range. The time domain spectra characteristic of photon-phonon interaction were presented and it show that the phonon polariton arises in BGO crystal.