Investigation of neutral atom and ion emission during laser conditioning of multilayer HfO₂-SiO₂ coatings

Conference · Sat Jun 01 00:00:00 EDT 1991 · Proceedings of SPIE - The International Society for Optical Engineering

DOI:https://doi.org/10.1117/12.27553· OSTI ID:5900392

Schildbach, M. A. ^[1]; Chase, Lloyd L. ^[1]; Hamza, Alex V. ^[1]

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1. Lawrence Livermore National Laboratory (LLNL), Livermore, CA (United States)

It has been recently shown that the optical damage thresholds of multilayer coatings can be increased by up to a factor of two by conditioning the coating at laser fluences below the optical damage threshold. We have investigated the laser conditioning mechanism of HfO₂-SiO₂ coatings by observing the laser-induced emission of neutral constituents of the coatings during laser conditioning. We observe the ejection of Hf, Si and oxygen (O or O₂, or both) neutrals starting at fluences of about 10 J/cm², considerably below our measured unconditioned damage threshold of about 16-18 J/cm². We observed a threshold pulse fluence for laser conditioning, which is also about 10 J/cm². This identical threshold for neutral emission and laser conditioning suggests that the neutral emission is caused by the laser conditioning process. The emitted neutrals have extremely high kinetic energies, on the order of several tens of eV. On the basis of this information, we propose that the laser conditioning process is caused by microscopic damage that involves cracking of the coating layers, resulting in the ejection of the high-energy particles via a "fractoemission" process. This microscopic damage apparently raises the damage threshold by either reducing the absorption of coating defects or by relieving the thermal stresses that cause cracking, particle emission, and possible plasma formation by laser ionization of the neutrals.

• Research Organization: Lawrence Livermore National Laboratory (LLNL), Livermore, CA (United States)
• Sponsoring Organization: USDOE Office of Science (SC), Basic Energy Sciences (BES). Materials Sciences & Engineering Division (MSE)
• DOE Contract Number: W-7405-ENG-48
• OSTI ID: 5900392
• Report Number(s): UCRL-JC-105106; CONF-9010287-7; ON: DE91009749
• Journal Information: Proceedings of SPIE - The International Society for Optical Engineering, Vol. 1441; Conference: 22. Boulder Damage Symposium, Boulder, CO (United States), 24-26 Oct 1990; ISSN 0277-786X
• Publisher: SPIE
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
HAFNIUM OXIDES
PHYSICAL RADIATION EFFECTS
SILICON OXIDES
ABSORPTION
ATOMS
CRACKS
DAMAGE
DEFECTS
ELECTRIC FIELDS
ELECTRONIC STRUCTURE
EXPERIMENTAL DATA
HAFNIUM
IMPURITIES
ION EMISSION
IONIZATION
IRRADIATION
LASER RADIATION
LAYERS
OXYGEN
REFLECTIVE COATINGS
SILICON
SUBSTRATES
THERMAL STRESSES
CHALCOGENIDES
COATINGS
DATA
ELECTROMAGNETIC RADIATION
ELEMENTS
HAFNIUM COMPOUNDS
INFORMATION
METALS
NONMETALS
NUMERICAL DATA
OXIDES
OXYGEN COMPOUNDS
RADIATION EFFECTS
RADIATIONS
REFRACTORY METAL COMPOUNDS
SEMIMETALS
SILICON COMPOUNDS
STRESSES
TRANSITION ELEMENT COMPOUNDS
TRANSITION ELEMENTS
360605* - Materials- Radiation Effects