STP799

    A Technique for Increasing the Optical Strength of Single-Crystal NaCl and KCl Through Temperature Cycling

    Published: Jan 1983


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    Abstract

    This paper relates a technique for increasing the optical strength of NaCl and KCl single-crystal samples. The 1.06-μm pulsed laser damage thresholds were increased by factors as large as 4.6 for some bulk NaCl single crystal, namely the laser grade NaCl purchased from Harshaw Chemical Company. The bulk laser damage breakdown threshold (LDBT) of the crystal was measured prior to and after heat treatment using a Nd:YAG laser operating at 1.06 μm in the TEMoo spatial mode with a pulse width of 9 nsec, full width at half maximum. After the LDBT of the untreated sample was measured, it was mounted in a quartz tube and placed in an oven for the heat treatment. The quartz tube was continuously flushed with dry nitrogen gas throughout the heat treatment cycle. The sample was slowly heated to a predetermined annealing temperature: for NaCl, up to 800°C (approximately 1°C below its melting temperature). The sample was maintained at this temperature for a short time and was then removed from the oven to allow rapid cooling. Samples taken to near-melt temperature required repolishing because of surface sublimation, which occurs at elevated temperatures. After repolishing, the bulk LDBT was remeasured and found to be up to 4.6 times greater than the value measured for the untreated crystal. For samples annealed at lower temperatures, bulk and surface LDBT's were studied; for cleaved and polished surfaces, changes in the damage morphology were found.

    Keywords:

    annealing, baking, bulk, damage threshold, potassium chloride, single crystal, sodium chloride, surface


    Author Information:

    Franck, JB
    Michelson Laboratory, Physics Division Naval Weapons Center, China Lake, California

    Soileau, MJ
    Michelson Laboratory, Physics Division Naval Weapons Center, China Lake, California


    Paper ID: STP37233S

    Committee/Subcommittee: F01.02

    DOI: 10.1520/STP37233S


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