Taking the shine off copper. Amin Abdolvand and his collaborators at the University of Dundee in the UK have discovered that intense nanosecond pulses of laser light can transform copper’s characteristically lustrous surface to a deep, absorbent black. Although the Dundee team conducted its experiments in air, oxidation or some other chemical reaction is not the transformation’s principal cause. Rather, the pulses modified the surface’s vertical structure through laser-induced melting and ablation. Achieving the effect depends on how the pulses are delivered. Abdolvand and his colleagues used a neodymium-doped yttrium orthovanadate laser, which emitted 12-ns pulses at a repetition rate of 30 kHz. When focused on the Cu surface, each pulse delivered 2.6 J/cm2 to a spot about 60 µm wide. Stepping the beam over the surface ensured that the modification took the form of discrete patches arranged in a closely spaced grid. As the accompanying figure shows, the...

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