• Research Areas
• Glasses and Amorphous Oxides
  • Aluminosilicate Glass Structure
  • Borosilicate Glass Structure
  • Pressure effects on glass and melt structure
  • Insulating coatings for microelectronics
  • Amorphous metal oxides for optical coatings
• Order/Disorder in Minerals and Ceramic Materials
• Dynamics in Crystalline and Molten Silicates and Oxides

Amorphous metal oxides for optical coatings

High-performance mirrors in optical systems are often made of a stack of alternating thin layers of amorphous oxides with high and low refractive indices, which can give extremely high reflectivity for a very narrow frequency range. The low index material is commonly silica, which is relatively well understood; the high index material is typically an amorphous oxide of a heavy metal such as tantalum. In part because the latter cannot be formed by conventional glass-forming methods, their atomic-scale structures are poorly known. Applications of NMR to such materials have been limited because the heavy metals involved (e.g. Ta) may not provide informative spectra. However, the NMR-active isotope of oxygen (17O) can in principle be incorporated into any oxide, providing a potentially very useful window on short-range structure. In a collaboration led by Stanford Applied Physics colleagues Robert Byer and Martin Fejer, focused on the next generation Laser Interferometer Gravitational Wave Observatory (LIGO), we are currently working to make 17O-enriched Ta2O5 thin films and constrain their structures by NMR. The goal is better understanding and eventually optimizing their properties to improve interferometer mirror performance.