Dielectric response function of CdF2 single crystal in the THz–IR ranges

The dielectric response function of the high-purity CdF₂ crystal was determined based on the analysis of broadband transmission and reflection spectra in terahertz and far IR ranges. Absorption are mainly formed due to the superposition of the phonon contribution and many-particle mechanisms. Simultaneous analysis of the obtained spectra allow to expand the dynamic range necessary for calculating the parameters of both weak bands of many-particle processes and intense line of the optical phonon mode. Parameters of electric dipole first- and second order absorption processes in the THz–IR ranges were obtained using classical oscillator and coupled oscillator models. The spectra of the complex dielectric permittivity of CdF₂ were calculated. The total contribution to the permittivity from difference many-particle processes was 4 % of the contribution of optical phonon modes. Many-particle absorption leads to an increase in dielectric losses by 4–5 times in the THz range.