Structural changes in dielectric optical coatings induced thermally or by high energy pulsed laser irradiation have been studied by the non-destructive technique of Raman Spectroscopy. A two laser (damage, probe) arrangement was used to characterize the damage process in crystalline and amorphous TiO2 and Zr02 coatings on silica during irradiation and at longer times following the onset of damage. Raman measurements were also undertaken to assess the effects of coating phase and microcrystalline grain orientation on laser induced damage in Ti02. Results suggest that certain phases have higher damage thresholds for comparable coating thicknesses and that thermal and electronic excitation effects are important considerations for modeling the damage process.
G. J. Exarhos,
P. L. Morse,
"Raman Studies Of Laser Damaged Single- And Multi-Layer Optical Coatings", Proc. SPIE 0540, Southwest Conf on Optics '85, (20 November 1985); doi: 10.1117/12.976152; https://doi.org/10.1117/12.976152