Laser-induced damage investigation in chirped mirrors for ultrashort pulse laser systems

The development of ultrashort pulse laser systems is strongly gaining of importance in laser technology and its applications. In the course of the achievements in laser development during the last years, reliable table-top ultrashort pulse laser systems are near to their realization. These systems will allow for innovative applications in industrial environments and medicine. For the next generation of ultrashort laser systems with pulse durations below 100 fs, chirped mirrors are employed for compensating pulse broadening induced by pulse propagation through laser crystals. In former investigations, a significantly lower damage threshold compared to standard mirrors was reported. At the Laser Zentrum Hannover, multiple-pulse laser-induced damage thresholds were determined with a measurement facility utilizing a Ti:Sapphire-CPA system. In the damage tests, samples coated with model layer systems, short pass filters, standard quarter-wave stacks and chirped mirrors were investigated. For the chirped mirrors, distinctly lower damage thresholds were measured compared to standard QWOT-mirrors. Calculations indicate a clear correlation between the damage threshold and the field intensity in the layer stacks.