Laser damage and ablation of differently prepared CaF2(111) surfaces
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Ablation thresholds and damage behavior of cleaved and polished CaF2(111) surfaces produced by single shot irradiation with 248 nm/14 ns laser pulses have been investigated using the photoacoustic mirage technique and scanning electron microscopy. The standard polishing yields an ablation threshold of typically 20 J/cm2. When surfaces are polished chemo-mechanically the threshold is raised to 43 J/cm2. Polishing by diamond turning leads to intermediate values around 30 J/cm2. Cleaved surfaces possess no well-defined damage threshold. The damage topography of conventionally polished surfaces shows ablation of flakes across the laser heated area with cracks along the cleavage planes. In the case of chemo-mechanical polishing only a few cracks appear. Diamond turned surfaces show small optical absorption, but cracks and ablation of tiles. The origin of such different damage behavior is discussed.
KeywordsCaF2 Laser Spot Damage Threshold Ablation Threshold Damage Behavior
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