Effect of Zinc Fluoride addition on structure of barium Borate glasses for nonlinear optical applications

Abstract A series of Zinc Barium Borate Oxyfluoride glasses with composition 60B2O3-(40-x)BaO-xZnF2, where x = 0, 10, 20, 30, and 40 mol% are prepared using the conventional melt quench method. Density and molar volume was found to decrease with the increase in ZnF2 content. The optical band gap was found to vary between 5.76 and 5.14 eV. Such a wide bandgap of the prepared samples makes them a potential candidate as Supercontinuum sources. Fourier transform infrared (FTIR) and Raman spectroscopy were used together to see the structural changes incurred in the material. Raman spectroscopy confirms the Non-bridging Oxygen variation while FTIR gives insights into borate structural units' changes, including the Boron coordination. Non-bridging Oxygen species were found to decrease initially with the addition of ZnF2 and thereby cause network loosening. FTIR studies indicate a nonlinear variation in the coordination of Boron with the addition of ZnF2. Nonlinear absorption and refraction have been measured to establish the potential of the prepared samples as supercontinuum sources. The origin of nonlinearity in the samples is explained from the insights obtained using structural investigations.