New solid-state lasers and their application potentials

In recent years, Nd:YAG-lasers have found increasing interest in many fields of high-power applications that formerly had been the domain of CO2-lasers. This was mainly due to several consequences of their wavelength, such as a higher absorptivity, lower sensitivity against laser-induced plasmas and, in particular, the use of flexible glass fibres for beam handling. Disadvantages like poor beam quality and low efficiency are being effectively reduced by recent developments of diode-pumped systems. Some promising concepts based on different pumping techniques and crystal geometries - rods, discs, fibres - will be discussed in view of attainable beam quality and means of power scaling. The second part of the paper will deal with investigations aimed at utilizing the beneficial properties of Nd:YAG-lasers. especially for welding. In particular, the advantages of the twin-focus technique are discussed in some detail with regard to power scaling, process improvements and flexibility increase. Based upon experience, the extension to a multi-focus technique is proposed by presenting experimental data obtained with lamp-pumped high-power lasers and results of numerical modelling. This evidence demonstrates the potential for industrial applications and provides an idea of what can be expected from the new generation of diode-pumped solid-state lasers with high beam quality. (C) 2001 Elsevier Science Ltd. All rights reserved.