A new composition of germanosili-cate glass created by adding zinc oxide has properties good for lens applications. The new family of zinc germanosilicate glass has a high refractive index comparable to that of pure germania glass. Samples showed high transparency, good ultraviolet-shielding properties, and good glass forming ability, making them suitable for lens applications. Germanosilicate glass is essential in the manufacture of optical amplifiers, waveguides, and solid-state lasers.
The refractive index of glass determines its use. The benefit of a high-refractive index is its capacity for designing low-thickness lenses. In glass synthesis, however, achieving a high refractive index typically has a few roadblocks. Lead oxide can accomplish this but requires the use of toxic raw materials. Non-lead constituents that encourage a high refractive index can make the glass much more difficult to form or prone to crystallization and therefore more opaque. By finding the optimum balance of zinc oxide with the other components of the glass composition, these issues were avoided.
Zinc oxide showed UV shielding properties in the study samples; this was expected given that inorganic sunscreen is based on zinc oxide. With UV shielding, a zinc-oxide-containing glass could be used for everyday applications such as car windows or eyeglasses.
The glass samples also showed favorable forming properties. As a “long glass,” the new compositions can be formed over a broader temperature range, making them much simpler to manipulate during formation. This property, the resistance to crystallization, and the lower cost of zinc oxide compared to germania all make the new glass composition a practical choice for manufacturing on a mass scale.