Models for the thermal expansion coefficient and temperature coefficient of the refractive index in gradient-index glass

In gradient-index glass the variation of glass composition can also cause a variation in the thermal properties across the gradient region. The difference in thermal expansion and dn/dT across the gradient-index region has been modeled. Several examples illustrate how the models can be utilized to select gradient-index glass compositions that will have constant thermal properties within the gradient region. Experimental measurement of the variations of αL and dn/dT in gradient-index glass is presented in a separate paper.