Mechanism for atmosphere dependence of laser damage morphology in HfO{sub 2}/SiO{sub 2} high reflective films
- Fine Optical Engineering Research Center, Chengdu 610041 (China)
- Department of Materials Science, Sichuan University, Chengdu 610064 (China)
We show in this paper single-shot and multi-shot laser-induced damage thresholds (LIDTs) of HfO{sub 2}/SiO{sub 2} high reflective films (the reflectance = 99.9%) are affected by the presence of a water layer absorbed on the surface of the porous films. When the water layer was removed with the process of pumping, the single-shot LIDT measured in vacuum dropped to {approx}48% of that measured in air, while the multi-shot LIDT in vacuum dropped to {approx}47% of its atmospheric value for the high reflective films. Typical damage micrographs of the films in air and in vacuum were obtained, showing distinct damage morphologies. Such atmosphere dependence of the laser damage morphology was found to originate from that formation of a water layer on the surface of porous films could cause an increase of horizontal thermal conductivity and a reduction of vertical thermal conductivity. Moreover, laser-induced periodic ripple damages in air were found in the SiO{sub 2} layer from the micrographs. A model of deformation kinematics was used to illustrate the occurrence of the periodic ripple damage, showing that it could be attributed to a contraction of the HfO{sub 2} layer under irradiation by the 5-ns laser pulses in air.
- OSTI ID:
- 22089335
- Journal Information:
- Journal of Applied Physics, Vol. 112, Issue 2; Other Information: (c) 2012 American Institute of Physics; Country of input: International Atomic Energy Agency (IAEA); ISSN 0021-8979
- Country of Publication:
- United States
- Language:
- English
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