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.