Calculations and experimental demonstration of multi-photon absorption governing fs laser-induced damage in titania.

Laser damage phenomena are governed by a number of different effects for the respective operation modes and pulse durations. In the ultra short pulse regime the electronic structure in the dielectric coating and the substrate material set the prerequisite for the achieved laser damage threshold of an optical component. Theoretical considerations have been done to assess the impact of contributing ionization phenomena in order to find a valid description for laser-induced damage in the femtosecond (fs) domain. Subsequently, a special set of sample has been designed to verify these considerations via ISO certified laser damage testing. Examining the theoretical and experimental data reveals the importance of multi-photon absorption for the optical breakdown. For titania, the influence of multi-photon absorption has been clearly shown by a quantized wavelength characteristic of the laser damage threshold.