Date of Award
Doctor of Philosophy (PhD)
Materials Science and Engineering
Chalcogenide glasses (ChGs) are well-known for their attractive optical properties, such as high refractive index and transparency in across infrared wavelengths. ChGs also possess the ability to compositionally tune properties such as the refractive index, the thermo-optic coefficient, and other non-optical properties. Chalcogenide glasses with compositionally tailored physical and optical properties will provide optical designers with new materials necessary to create novel infrared imaging systems requiring new or expanded functionality. This dissertation has evaluated the relationship between glass composition, the resulting atomic structure, and resulting optical and thermo-optical properties, with specific focus on the infrared refractive index and the thermo-optic coefficient (dn/dT). To create these linkages, a series of GeAsSe glasses with increasing Ge content were fabricated across three tielines, and evaluated for their chemical and physical attributes. A novel infrared refractometer was constructed to provide supplemental refractive index and dn/dT data. Findings in this dissertation showed a correlation between the Ge content of the glass composition and several non-optical properties. Namely, as the Ge content increases, the glass transition temperature and Vickers Hardness increase, while the coefficient of thermal expansion decreases. These physical changes are due to the cross-linking of the glassy network by the 4-coordinated Ge additions. In contrast, optical property data showed a strong dependence on the appearance and/or disappearance of specific atomic structures within the glassy network as the glass composition changes. Overall, this study aimed to answer key questions that have not been systematically studied within multi-component chalcogenide glasses. These questions include: â€¢ How will compositional variations for the sake of optical tunability affect the physical properties which dictate a materialsâ€™ response to manufacturing processes? â€¢ Are there links between optical properties, such as the index and dn/dT, and non-optical properties that can allow for easier prediction of the difficult to measure optical properties? â€¢ Are there compositions within the GeAsSe ternary that can produce a zero dn/dT that will offer better thermo-mechanical stability to the current commercial options? Finally, this work presented a new phenomenon of a thermally-induced, sub-Tg index hysteresis and subsequent room temperature structural relaxation in chalcogenide glasses. This process resulted in a maximal change in the room temperature refractive index of 0.0030. Over the course of 2 months the structural relaxations returned the refractive index to the initial state, with a characteristic relaxation time ranging from Ï„ = 70,000s to Ï„ = 300,000s.
Gleason, Benn, "Designing Optical Properties in Infrared Glass" (2015). All Dissertations. 1568.