Thermo-optic coefficients of potassium alumino-metaphosphate glasses Original Research Article

Metaphosphate compositions of the K2O–Al2O3–P2O5 system have been melted and their properties measured to assess their potential for athermalisation. The results show that the addition of alumina (Al2O3) increases the refractive index and glass transition temperature (Tg), decreases the thermal expansion coefficient (α) and leads to a more positive thermo-optic coefficient (dn/dT). Glasses must exhibit negative dn/dT as a requirement for athermalisation purposes.