Novel optical concept for line beam optics for large area thermal processing

Abstract

With the availability of high-power infrared laser sources, the thermal processing of large area substrates with lasers becomes increasingly attractive. Besides the laser source, one of the core components is the beam shaping optics for the generation of a line-shaped intensity profile with an extreme aspect ratio.We report on a novel optical concept for laser-based large area thermal processing based on the thin disk laser platform providing output power in excess of 10 kW per unit. The most unique feature of this novel modular concept is the capability to precisely combine several optical units in order to realize a beam profile with a width of less than 100 µm and a length of more than 3 m.In order to meet the high demands on homogeneity and depth of focus we make use of advanced beam-shaping and measurement techniques. Combining the proven robustness of fiber-coupled laser sources with this modular optical approach, we demonstrated the ability of 24/7 operation with industrial standards in terms of process quality, treatment speed and efficiency. For the first time, rapid thermal annealing with high power lasers was applied to thin films deposited on jumbo-size architectural glass without affecting the glass substrate.The novel thermal treatment process results in a highly improved crystallization of the coating and correspondingly a reduction of the resistivity of e.g. thin Ag-based coating stacks by up to 30 %. This leads to a break-through in the development of high energy efficiency functional coatings on glass.The novel technology opens a large field of new cost-effective glass products with improved energetic balance, simultaneous high transparency and improved electronic transport properties and many others.Furthermore, the new beam shaping concept shows the potential for further heat treatment applications requiring intensity profiles with extreme aspect ratios, such as metal refinement, thermal treatment of metal surfaces or large area paint removal.