Dumping effect on the forming of negative dielectric properties in crystal

The physical conditions analysis for the appearance of negative values of the dielectric function (DF) within the T-L splitting frequency interval in polar crystals is presented. The simple quantitative criterion for existence of negative DF band is derived in the three equivalent forms as a proper combination of basic parameters of a single phonon vibration. Principal significance of the phonon damping will be demonstrated in report especially for the realization possibility for the wave penetration process of in the negative dielectric region. It is shown the phonon damping may transform the wave to evanescent type in the negative dielectric area or moreover it may also cause the collapse of the transmitted wave in a narrow layer near the crystal surface, several times less than the wavelength of incoming radiation.