Pockels Coefficients in Multicomponent Oxide Glasses

In this work, a corrected model for the additivity of the Pockels coefficients in multicomponent oxide glasses is derived. Given some material deformation, changes in density and electronic polarizability are known to be the dominant factors in the photoelastic effect. A trend of Pockels coefficients decreasing with increasing bond ionicity is postulated. This is discussed and shown to be due to the balancing of the relative changes in density and in polarization based on the bond strength and directionality. Alkali silicate data taken from the literature, shown to oppose the observed trends, is analyzed and compared to alkaline earth silicate data. The opposing trend is shown to be due to the bonding of the modifier ions. The alkali ions, associated with a single nonbridging oxygen (NBO), yield an increased relative density change and a decreased relative change in polarization. The alkaline earth ions, being associated with two NBOs, as expected experience significant density and polarizability changes that are more spatially distributed. Greater insights into the structural and chemical origins of the Pockels coefficient in multicomponent oxide glasses will enable the development of new optical fibers for high energy laser applications where photoelasticity-influenced parasitic effects such as stimulated Brillouin scattering are mitigated.