STP759

    Deformation of Intense Laser Beams Tightly Focused Inside NaCl: A Comparison of the Multiphoton-Polaron and Avalanche Models of Optical Breakdown

    Published: Oct 1981


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    Abstract

    Computer simulations of the interaction of intense picosecond laser pulses (λ = 532 nm) with NaCl in the focal volume of a 2.54 cm focal length aberration-free lens indicate that severe beam deformation may take place at photon fluxes corresponding to the single-shot damage threshold measured under these experimental conditions. This deformation is the result of a change in the dielectric function which, in turn, is caused by free carriers generated via multiphoton-assisted avalanche ionization and/or multiphoton absorption. Strong self-defocusing prevents local photon fluxes from reaching values required to raise the lattice temperature sufficiently for damage to occur. We conclude that either both the avalanche ionization as well as the multiphoton-polaron absorption mechanisms of laser breakdown are invalid in their present form or that the experimentally determined damage thresholds do not pertain to the intrinsic properties of NaCl.

    Keywords:

    Avalanche breakdown, Beam deformation, Beam depletion, Free carrier absorption, Multiphoton absorption, Polaron absorption


    Author Information:

    Kelly, P
    National Research Council, Ottawa,

    Ritchie, D
    National Research Council, Ottawa,

    Braunlich, P
    National Research Council, Ottawa,

    Schmid, A
    National Research Council, Ottawa,

    Bryant, GW
    National Research Council, Ottawa,


    Paper ID: STP37031S

    Committee/Subcommittee: F01.02

    DOI: 10.1520/STP37031S


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