Raman Spectra and Structure Analysis of LIGO Coating Amorphous Oxides

Ti-doped GeO2 amorphous oxides are a promising candidate for mirror coatings in near future LIGO experiments. Raman spectroscopy is sensitive to local vibrations of structures with short- and medium-range order found in glasses. To explore local structure we calculate Raman spectra of Ti doped GeO2 samples with various doping percentages ranging from 10% to 50% via first-principles density functional theory. Structure analysis applied to those samples enables us to relate each Raman peak with particular atomic movements. Differences in Raman spectra of annealed and as-deposited samples show the changes in local structure for samples prepared using different methods. A few machine learning techniques are also implemented, with varying success, to identify the structural features important in Raman calculations.