Damage Thresholds to Metal Mirrors by Short-Pulse CO2 Laser Radiation

Figueira, J. F.; Thomas, S.J.; Harrison, R. F.

doi:10.1520/stp37245s

Cited by 3 publications

References 4 publications

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Multiple-Pulse Laser-Induced Damage To Metal Mirror Surfaces

1988

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The accumulation dependence of damage and laser induced damage morphologies on single crystal metal surfaces have been observed under Q-switched 1064 nm Nd:YAG laser irradiation at 10 nsec pulses at a 10 Hz rate. Several different damage morphologies were observed: slip -line formation, ripple patterns, flat -melting, and boiling. Damage probability versus fluence curves and accumulation curves are plotted to investigate damage behavior as it correlates with morphology. Accumulation curves showed different damage behavior for crystals of different orientation. Threshold decrease due to accumulation was the largest on (111) Cu and Al surfaces, whidh also had the lowest single shot damage threshold. The threshold reduction in accumulation follows the equation FN = F1 NS-1 where FN is the N -pulse damage threshold, N the pulse number, and S the slope of the accumulation curve. Accumulation appears to be the result of the storage cycle of thermal stress -strain energy induced by each laser pulse, and multi -pulse damage results from plastic slip and fatigue.

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Multiple-Pulse Laser-Induced Damage To Metal Mirror Surfaces

1988

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Damage Morphologies and Cumulative Behavior of Laser Damage on Single Crystal Metal Surfaces

Jee

Becker

Walser

1988

Laser Induced Damage in Optical Materials: 1986

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We have observed laser induced damage morphologies and the accumulation dependence of damage on single crystal metal surfaces under Q-switched Nd:YAG laser irradiation (1064 nm, 10 nsec pulses with a 240 μm spot diameter). The samples were chemically-polished copper and electro-polished aluminum of several crystallographic orientations. Several different damage morphologies have been observed: slip-line formation, ripple patterns, flat-melting, and boiling. Damage probability versus fluence curves and accumulation curves were plotted to investigate damage behavior as it correlates with morphology. Flat-melting damage was observed near the 50% damage fluence on chemically polished copper surfaces, and slip-lines were found near the 50% damage fluence on electropolished aluminum surfaces. Surface defects produced during sample preparation greatly influenced the damage threshold of copper because of its high melting threshold. The influence of surface defects on copper decreased with increasing numbers of laser pulses. Accumulation curves show different damage behavior for crystals of different orientation. Accumulation was the largest on (111) Cu and Al surfaces, and the single shot damage threshold of these surfaces was less than the other crystal orientations for both Cu and Al.

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