THERMOOPTIC COEFFICIENTS OF SOME STANDARD REFERENCE MATERIAL GLASSES

The thermooptic coefficients, i.e., the change in refractive index with temperature (dn/dT), of four National Institute of Standards and Technology standard reference material (SRM) glasses have been measured over the range of 25-degrees to 125-degrees-C. The thermooptic coefficients of all four glasses, NBS-710 (a soda-lime silicate), SRM-711 (a lead silicate), SRM-717 (a borosilicate), and SRM-739 (silica) are positive and range in value from 2 x 10(-6)/K to 9.8 x 10(-6)/K. The differences in the dn/dT of these glasses arise from differences in the coefficient of thermal expansion and the temperature coefficient of the electronic polarizability.