International audienceAn experimental and numerical study of the laser-induced damage of the surface of optical materialin the femtosecond regime is presented. The objective of this work is to investigate the differentprocesses involved as a function of the ratio of photon to bandgap energies and compare the resultsto models based on nonlinear ionization processes. Experimentally, the laser-induced damagethreshold of optical materials has been studied in a range of wavelengths from 1030 nm (1.2 eV) to310 nm (4 eV) with pulse durations of 100 fs with the use of an optical parametric amplifier system.Semi-conductors and dielectrics materials, in bulk or thin film forms, in a range of bandgap from 1to 10 eV have been tested in order to investigate the scaling of the femtosecond laser damagethreshold with the bandgap and photon energy. A model based on the Keldysh photo-ionizationtheory and the description of impact ionization by a multiple-rate-equation system is used toexplain the dependence of laser-breakdown with the photon energy. The calculated damage fluencethreshold is found to be consistent with experimental results. From these results, the relativeimportance of the ionization processes can be derived depending on material properties and irradiationconditions. Moreover, the observed damage morphologies can be described within the frameworkof the model by taking into account the dynamics of energy deposition with one dimensionalpropagation simulations in the excited material and thermodynamical considerations

Laser-induced damage is defined as any permanent laser-induced change in the characteristics of a sample. This change can be observed by many different inspection techniques, with different sensitivity, depending on the intended objectives and available techniques. The damage threshold definition and measurement are therefore very subjective and related to the detection method. The choice and implementation of a damage test system is then a critical issue on any experiment. In this work we present some implementation of detection techniques for laser damage metrology in the sub-picosecond regime. Different damage testing methods that have been applied will be discussed in view of their potential applications for testing functional optical components or to study physical process in the femtosecond regime, particularly the role of defects: optical microscopy, phase microscopy and time-resolved microscopy.