Compositional Trends in Photoelastic Constants of Borate Glasses

The stress-optical coefficients of binary and ternary borate glasses were measured and the factor ( p·q ), where p and q are the Neumann strain-optical coefficients, was determined. As a modifier oxide was added to B₂O₃ glass, the stress-optical coefficient decreased monotonically. It was found that the stress-optical coefficient is determined mainly by the elastic modulus, but the factor ( p·q ) becomes significant when the content and polarizability of the modifier cation are high. It was also found that the factor ( p·q ) decreases when the content and polarizability of the modifier cation increase. The ( p·q ) was divided into the lattice effect and the atomic effect, and their compositional dependences were discussed.