On Matumura

Spectral Emission by Polaritons in LiF

The upper branch of the polariton dispersion curve has been experimentally obtained by measuring the thermal emission spectra of thin films of LiF at oblique emission angles. The formulation based on the virtual mode theory is given for determination of the dispersion relation. The dispersion curve has been obtained from the resonance frequency and width of the thermal emission due to 0 T H mode which is the lowest mode at higher frequency region than LO frequency. Measurements have been performed at temperatures 420°K and 650° and at emission angles ranging from 45° to 80°. The results agree fairly well with the theory.

Thermal-emission spectra of coagulated small MgO crystals

The thermal-emission spectra of small MgO cubes (about 0.1 μm) were measured in the frequency region of their surface phonon modes. From the partial derivative of emissivity with respect to particle density, the emissivity of an MgO coagulation has been determined as a function of frequency. With an assumption of spherical coagulation, it is concluded that the dielectric function of small MgO particles and its temperature dependence are nearly the same as those of a bulk crystal.

Spectral Emission by Polaritons in CaF_2 and MgO

Thermal emission spectra measurements of thin films were made from 400 to 1100 cm -1 -1 for CaF 2 and from 400 to 1300 cm -1 for MgO at emission angles ranging from 10° to 80° and at temperatures 470 K and 605 K. The observed emission peaks near the frequencies of long wavelength longitudinal optical( L O ) modes, which are a function of sample thickness and emission angle, are explained by the virtual mode theory. The upper branch of the polariton dispersion curve and the polariton lifetime were experimentally determined by analyzing the observed emission peaks due to the 0 T H virtual mode which is the lowest mode in high frequency region with respect to the L O frequency. The linewidth of the polariton arising from the lattice anharmonicity was obtained by subtracting the width due to the radiation damping of 0 T H mode from the observed width. The results agree fairly well with the theoretical curve of the damped polariton.