Photothermal microscopy for the study of laser damage initiation by measurement of absorption modification of silica seeded with gold nanoparticles

In order to understand the mechanisms of laser damage initiation, we study “model” samples constituted of pure silica seeded with 3 nm gold particles. Numerical simulations are performed with a 1-D hydrodynamic code to determine the laser light absorption by a spherical nanoparticle. This code also simulates the thermal conduction, radiative transfer and ionization by UV light emitted by the heated metallic particles. The setup used for experimental studies is a high resolution, high sensitivity photothermal microscope. This setup allows correlation between optical absorption and laser irradiation. We observe the silica transformation in terms of absorption modification as a function of the irradiation fluence. The morphology of irradiated samples surface is observed thanks to “Nomarski” and “atomic force” microscopy and compared to photothermal microscopy results. A correlation is observed between flaked silica and strongly absorbing areas.