(in German)

Beside the total laser power, the laser beam diameter is a significant factor for the resistance of laser protection filters to laser radiation. In this report a study of the resistance of laser protection filters to laser radiation in dependence of the laser beam diameter is given. For the investigation of this effect an experimental setup was realized, which detects laser radiation near the MPE value (Henderson, et al., 2004) (Maximum Permissible Exposure; level of laser radiation to which, under normal circumstances, persons may be exposed without suffering adverse effects) behind the filter glasses, which was taken as a criteria for the failure of laser protection filters. This failure defines the laser resistance time of the protection filter under the given laser parameters (laser power and laser beam diameter). The experiments involved a number of laser irradiation tests with a cw (continuous wave) Nd:YAG laser (wave-length 1064 nm), a cw ytterbium fiber laser (1070 nm), pulsed Nd:YAG lasers (1064 nm and 532 nm) and a CO₂ laser (10600 nm), varying laser parameters such as power and beam diameter. The found dependencies of the laser resistance time versus laser beam diameter follow within the investigated laser parameter area different functions, such as a power function in the case of polymethyl methacrylate (PMMA) laser protection filters on the laser irradiation at 1064 nm in cw mode. The investigations show in this case that it is possible, by applying a simple empirical model, to calculate the laser resistance time for different laser beam diameters for a specific laser safety filter type (PMMA at 1064 nm) by only performing a few specific laser resistance tests within a fixed laser parameter area. The observed experimental results are reproduced in part by a physical model with a COMSOL Multiphysics® simulation.

Please download the complete report "Safety of laser protection filters as a function of beam diameter" (in German only).