STP1141

    Multiple-Pulse Damage of BK-7 Glass

    Published: Jan 1991


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    Abstract

    High power glass laser systems for laser fusion use many BK 7 glasses, and the laser induced damage of this glass is a serious problem. Since the BK 7 glass is generally melted in platinum (Pt) crucibles, the laser damage due to metallic Pt particles occurs inside the glass. The Pt particles cause fractures when irradiated at a fluence higher than 3 J/cm2 with 1064 nm, 15 ns laser pulse. The size of the fracture increases with irradiation fluence, and the damaged glass has to be replaced.

    In special cases, BK 7 glass is melted in ceramic crucibles, but there is a problem of cristobalite production inside the BK 7 glass. The laser damage threshold of cristobalite is about 4.5–5.5 J/cm2 with 1064 nm, 15 ns laser pulse.

    We have found average damaged particles in BK 7 glasses melted in Pt and ceramic crucibles to be 200–400 and ̃ 10 particles per liter, respectively. At present, laser damage in BK 7 glass is being improved by changing a composition ratio of melting materials.


    Author Information:

    Yoshida, K
    Institute of Laser Engineering, Osaka University, Osaka,

    Yoshida, H
    Institute of Laser Engineering, Osaka University, Osaka,

    Noda, T
    Institute of Laser Engineering, Osaka University, Osaka,

    Nakai, S
    Institute of Laser Engineering, Osaka University, Osaka,


    Paper ID: STP23606S

    Committee/Subcommittee: F01.02

    DOI: 10.1520/STP23606S


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