Levitators Offer High-Performance Glasses

Researchers at the Glass Products Div. of Containerless Research Inc. of Evanston, Ill., are producing new rare-earth-doped glasses that have applications in high-power-density solid-state lasers, telecommunications, medical lasers, military and security technologies, and optical components. The use of levitation systems at NASA's Marshall Space Flight Center in Huntsville, Ala., that offer a perfectly uncontaminated environment enabled the development of the glasses, which are available in commercial quantities made to customer specifications.

Called REAl Glass, the material features a high concentration (up to 50 percent) of optically active rare-earth oxides in an aluminum oxide and silicon dioxide host. It displays a refractive index of 1.7 to greater than 1.8, infrared transmission to 5.5 µm, an Abbe constant of 40 to 60 and a hardness of 800 to 1100 Vickers. The rare-earth oxides are added to the material singly or in combination to achieve the desired optical characteristics.

Crucial to the production of REAl Glass is the levitator. The researchers employed an electrostatic apparatus at the NASA facility. Such an approach isolates a molten specimen in midair to prevent any undesired chemical or physical interaction with its surroundings. Focused laser beams serve as heating elements.

Potential uses for the glasses include active media in high-power lasers for materials processing and marking and sealing, optical amplifiers and planar waveguide components in telecommunications, IR windows and high-index/low-dispersion lenses. Application development is being performed with support from the National Science Foundation's Small Business Innovation Research grant program.