The splitting between longitudinal and transverse optical modes was observed in the infraredreflection spectra of silica glasses at different incident angles. The density of states and thefrequency of the longitudinal mode were found to increase with increasing incident angle. A sharpminimum in the reflectance was monitored at large incident angles. A transmission window wasobserved in the absorption spectra of silica glass plates. The sharp minimum in the reflectance andappearance of the transmission window are believed to be the results produced by the Doppler effectdue to the interaction of longitudinal and transverse optic modes in silica glass. The phase velocityof the longitudinal mode was evaluated in terms of the relativistic Doppler shift formula.

Depolarization experiments were performed on silica glasses (Suprasil 2 and Suprasil W2) to the glass transitiontemperature. Crystal-like microstructures were observed to exist in silica glasses. The phase transitions were monitoredwhich correspond to a-cristobaliteMb-cristobalite, a-quartzMb-quartz, b-quartzMb-tridymite, and a-tridymiteMb-tridymite. The depolarization intensity of polarized He

Optical interference was observed in a silica glass plate (Suprasil W2) and air/silica glass/a-Si-thin

X-ray diffraction measurements were performed on silica glasses permanently densi

Densities, refractive indices, and IR (re