Since the average power of ultrafast lasers is increasing continuously, thermal effects in laser optics cannot be neglected anymore. When the thermal refractive power of a laser optics (e.g. focusing optics) is known, the distance between the focusing optics and the workpiece can be adapted to ensure a fault-free processing result.
As part of the BMBF-project SCULPT, the IFSW hast determined the thermal refractive power of laser optics, from which the thermally induced focal shift can be calculated. Thin lenses made of different substrates (N-BK7 and fused silica) and with different coatings (uncoated, broadband coating and wavelength coating) were investigated. The type of coating can have a much larger influence than the substrate.
The results have been published at: https://doi.org/10.1364/OE.26.026020
Contact: Sebastian Faas und Dr. Rudolf Weber