Experimental Studies of Laser-Induced Breakdown in Transparent Dielectrics [electronic resource].

Published:: Washington, D.C. : United States. Dept. of Energy, 2003.
Oak Ridge, Tenn. : Distributed by the Office of Scientific and Technical Information, U.S. Dept. of Energy.
Physical Description:: PDF-FILE: 137 ; SIZE: 2.8 MBYTES pages
Additional Creators:: Lawrence Livermore National Laboratory, United States. Department of Energy, and United States. Department of Energy. Office of Scientific and Technical Information

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Summary:

The mechanisms by which transparent dielectrics damage when exposed to high power laser radiation has been of scientific and technological interest since the invention of the laser. In this work, a set of three experiments are presented which provide insight into the damage initiation mechanisms and the processes involved in laser-induced damage. Using an OPO (optical parametric oscillator) laser, we have measured the damage thresholds of deuterated potassium dihydrogen phosphate (DKDP) from the near ultraviolet into the visible. Distinct steps, whose width is of order K{sub b}T, are observed in the damage threshold at photon energies associated with the number of photons (3→2 or 4→3) needed to promote a ground state electron across the energy gap. The wavelength dependence of the damage threshold suggests that a primary mechanism for damage initiation in DKDP is a multi-photon process in which the order is reduced through excited defect state absorption. In-situ fluorescence microscopy, in conjunction with theoretical calculations by Liu et al., has been used to establish that hydrogen displacement defects are potentially responsible for the reduction in the multi-photon cross-section. During the damage process, the material absorbs energy from the laser pulse and produces an ionized region that gives rise to broadband emission. By performing a time-resolved investigation of this emission, we demonstrate both that it is blackbody in nature, and we provide the first direct measurement of the localized temperature during and following laser damage initiation for various optical materials. For excitation using nanosecond laser pulses, the plasma, when confined in the bulk, is in thermal equilibrium with the lattice. These results allow for a detailed characterization of temperature, pressure, and electron densities occurring during laser-induced damage.

Report Numbers:

E 1.99:ucrl-lr-155392
ucrl-lr-155392

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Dissertation Note:

Thesis (Ph.D.); Submitted to the Univ. of California, Davis, CA (US); PBD: 23 Sep 2003

Note:

Published through SciTech Connect.
09/23/2003.
"ucrl-lr-155392"
Carr, C W.

Funding Information:

W-7405-ENG-48

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