SEDL / STP / STP1015-EB / STP18780S

Thresholds Measured With 350-nm Pulses at 25–100 Hz for Bare Polished Crystals of CaF² and for Silica Sol-gel AR Coatings on Silica Substrates

Staggs, MC
Lawrence Livermore National Laboratory University of California, Livermore, California

Milam, D
Lawrence Livermore National Laboratory University of California, Livermore, California

Thomas, IM
Lawrence Livermore National Laboratory University of California, Livermore, California

Wilder, JG
Lawrence Livermore National Laboratory University of California, Livermore, California

Pages: 8    Published: Jan 1988

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Abstract

An XeF laser-damage experiment was used to measure damage thresholds for bare polished crystals of CaF² and porous silica antireflection coatings on fused silica substrates. Damage was induced by applying 1000 350-nm, 25-ns pulses at repetition rates of 25–100 Hz to small (typically 0.12 × .03 cm) sites on the surfaces of the sample. Eight samples of fluorescence-free CaF² exhibited both surface and bulk damage at fluences as low as 10 J/cm². Three samples of UV-grade CaF² also had surface damage thresholds of 10 J/cm², and bulk damage was not observed in this material. Thresholds for the porous silica coatings were 17–23 J/cm².