THE STRUCTURAL INVESTIGATION OF A ZBLAN GLASS BY VIBRATIONAL SPECTROSCOPY

The heavy metal fluoride glasses exhibit high transparency over the fr equency range from the mid-IR to the near UV. They also possess low re fractive index, low material dispersion, low linear scattering loss, a nd good chemical durability. These properties make them the promising candidate for a wide variety of applications ranging from laser window s to infrared fiber optics. The structural investigations of a typical heavy metal fluoride glass, ZBLAN, by vibrational spectroscopy (multi -phonon edge absorption, infrared reflectivity and polarized Raman sca ttering measurements) were performed. From our study, we are able to u nderstand the fundamental vibrational characteristics of this glass an d the primary mechanisms influencing its infrared transparency. The LO TO Vibrational pair splitting was observed for this glass by IR reflec tivity measurement at different incident angle. We believe that this t ype of crystal-like behavior is related to frozen in density and conce ntration fluctuations in the glass structure during the glass formatio n. The low frequency Raman spectrum (10 similar to 100 cm(-1)) - the s o called Boson Peak - was also studied for the same glass. The charact eristic length scale (Structural Correlation Length) was calculated wi th the aid of Martin-Brenig model. The degree of disorder in tile glas s structure will be discussed in the light of the existing theory.