Fabrication of GRIN Glass Spheres

A glass sphere, with a refractive index of 2.0 at the surface (a miniature sphere retroreflector, with diameter in the range of 1 to 5 mm) has a number of unique properties that make it attractive for many remote sensing applications, including radiation detection in support of the DOE¿s nonproliferation responsibilities. For example, these spheres can be deployed without concern of precise placement, because the spherical geometry provides an omni-directional return. Also, they easily can be deployed in large numbers, yet remain indistinguishable from the background environment. The DOE is seeking fabrication methods for Gradient Index (GRIN) glass spheres, 1 to 5 mm diameter, and with a potential minimum refractive index gradient of 0.2. One relatively inexpensive method of gradually increasing the refractive index of mm-scale glass spheres is to roll them into ceramic powders of selected properties, and then consolidate the agglomerate by thermal treatment. This project will use this technology to produce nearly defect-free mm-scale glass spheres. Commercial Applications and other Benefits as described by the awardee: In addition to the application to nuclear nonproliferation, the GRIN glass spheres should find use in applications that require microlenses with specific compositions.