Optimization of Laser-Damage Resistance of Evaporated Hafnia Films at 351 nm
A systematic study was undertaken to improve the laser-damage resistance of multilayer high-reflector coatings for use at 351 nm on the OMEGA EP Laser System. A series of hafnium dioxide monolayer films deposited by electron-beam evaporation with varying deposition rates and oxygen backfill pressures were studied using transmission electron microscopy (TEM), x-ray diffraction (XRD), and refractive index modeling. These exhibit microstructural changes for sufficiently slow deposition rates and high oxygen backfill pressures, resulting in an absence of crystalline inclusions and a lower refractive index. Hafnia monolayers exhibited laser-damage resistance as high as 12 J/cm^2 at 351 nm with a 0.5-ns pulse. This process was utilized in the fabrication of reduced electric-field-type multilayer high-reflector coatings. Measured laser-damage thresholds as high as 16.63 J/cm^2 were achieved under identical test conditions, an exceptional improvement relative to historical damage thresholds of the order of 3 to 5 J/cm^2.
- Research Organization:
- Univ. of Rochester, NY (United States). Lab. for Laser Energetics
- Sponsoring Organization:
- USDOE
- DOE Contract Number:
- FC52-08NA28302
- OSTI ID:
- 950855
- Report Number(s):
- DOE/NA/28302-881; 2008-74; 1859
- Journal Information:
- Laser-Induced Damage in Optical Materials: 2008, Vol. 7132; Conference: Boulder Damage Symposium, Boulder, CO, 22-24 September 2008
- Country of Publication:
- United States
- Language:
- English
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