Crystallization of fused silica surfaces by ultra-violet laser irradiation
- Sigma Koki Co., Ltd., 1-19-9 Midori, Sumida-ku, Tokyo 130-0021 (Japan)
In recent years, the increased use of high power lasers has created problems in optical elements due to laser damage. The International Organization for Standardization (ISO) describes in a publication ISO 11254 a laser-power resilience (LPR) test which we used to verify that by flattening the glass substrate of an optical element, we could improve the resistance to laser damage. We report on an evaluation of two types of samples of fused silica substrate whose surface roughness differed (R{sub a} = 0.20 nm and R{sub a} = 0.13 nm) using customized on-line laser damage testing. To induce laser damage to samples, we used the fifth harmonic generation from a Nd:YAG pulse laser (wavelength: 213 nm, pulse width: 4 ns, repetition frequency: 20 Hz). Results show that flattening reduced the progression of laser damage in the meta-phase laser damage phase by 1/3 of that without flattening. However, pro-phase laser damage which started at fluence 2.39 J/cm{sup 2} was unrelated to surface roughness. To analyze the pro-phase laser damage, we used x-ray diffraction (XRD), Raman spectroscopy, and variable pressure-type scanning electron microscopy (VP-SEM). From XRD data, we observed XRD patterns of cristobalite (111), cristobalite (102), {alpha}-quartz (111), and {beta}-quartz (102). Raman spectrum data showed an increase in the three-membered ring vibration (600 cm{sup -1}), four-membered ring vibration (490 cm{sup -1}), and many-membered ring vibration (450 cm{sup -1}, 390 cm{sup -1}, and 300 cm{sup -1}). We observed patchy crystallized areas on the sample surfaces in the VP-SEM images. Based on these experimental results, we believe that the dominant factors in pro-phase laser damage are their physical properties. Substrate and thin film material must be appropriately selected in producing an optical element with a high level of resilience to laser exposure.
- OSTI ID:
- 22089337
- 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
Similar Records
Evidence of Room Temperature Ferromagnetism in Zn{sub 1−x}Sn{sub x}S Thin Films
Thickness dependent structural, optical and electrical properties of CuIn{sub 0.8}Ga{sub 0.2}Se{sub 2} thin films deposited by pulsed laser deposition
Related Subjects
SUPERCONDUCTIVITY AND SUPERFLUIDITY
CRYSTALLIZATION
GLASS
HARMONIC GENERATION
LASER RADIATION
NEODYMIUM LASERS
QUARTZ
RAMAN SPECTRA
RAMAN SPECTROSCOPY
ROUGHNESS
SCANNING ELECTRON MICROSCOPY
SILICON COMPOUNDS
SUBSTRATES
SURFACES
ULTRAVIOLET RADIATION
WAVELENGTHS
X-RAY DIFFRACTION