Role of thermal history in the formation of commercial‐scale, infrared glass‐ceramics

The ability to translate melt properties and performance of small volume optical glass melts (i.e., melt sizes less than a few hundred grams) to manufacturable, commercial size melts (typically greater than 1 kg) requires a variety of processing optimization steps. Such melt size scale‐up often involves issues related to thermal properties of the composition and thermal history of the glass upon quenching, impacting the thermal, mechanical, and optical property homogeneity. In the present effort, we assess the viability of a complex, well‐studied, functional glass composition, (GAP‐Se) to evaluate the likelihood that commercial melts can be made to exhibit optical performance comparable to past lab‐scale melts. Such confirmation of property/performance metrics is required to satisfy the rigors of optical designer demands that can enable new solutions for infrared optical designs. We demonstrate that for GAP‐Se bulk glass subjected to controlled crystallization, measurable modification to the optical composite's effective refractive index can be achieved. Employing these data, we present viable mid‐wave infrared optical design results implementing a methodology suggesting how gradient refractive index elements from this material can be made with equivalent or improved size, weight, power, and cost.