The absorptance of metallic alloys to Nd:YAG and Nd:YLF laser light

Abstract: In Laser Material Processing of metals, an understanding of the fundamental absorption mechanisms plays a vital role in determining the optimum processing parameters and conditions. The absorptance, which is the fraction of the incident laser light which is absorbed, depends on a number of different parameters. These include laser parameters such as intensity, wavelength, polarisation and angle of incidence and material properties such as composition, temperature, surface roughness, oxide layers and contamination. The vast theoretical and experimental knowledge of the absorptance of pure elements with smooth, contamination-free surfaces contrasts with the relatively sparse information on the engineering materials found in real processing applications. In this thesis a thorough investigation of the absorption mechanisms in engineering grade materials has been started. The Licentiate thesis consists of 5 papers. Paper 1 is a short review of some of the most important mathematical models used in describing the interaction between laser light and a metal. Paper 2 is a review of a few experimental methods of measuring the absorptance of an opaque solid such as a metal. Papers 3 and 4 are experimental investigations of the absorptance of some of the most frequently found metallic alloys used in Laser Material Processing today. Paper 5 is a co-authored paper on the cleaning of copper artefacts with the use of second harmonic generated Nd:YAG laser light.