Emmanuel Hugonnot

Late-stage kinetics of laser-induced photochemical deposition in liquid solutions

Using a reaction-diffusion equation involving the one-photon excitation of a two-level system, we propose a rate equation that describes the late-stage growth of laser-induced photochemical deposits. With appropriate scaling, we show that the kinetics can be reduced to a single master curve for large beam radii. To experimentally illustrate the model, we investigate the coarsening of the deposit induced by a reaction with chromates photoactivated by a continuous Ar+ laser wave. Predicted growth laws are confirmed and the universal single-scaled dynamics is experimentally demonstrated.

Kinetics of surface relief gratings tailored by laser-induced photochemical deposition

We theoretically describe and experimentally explore the real-time formation of gratings induced by photochemical deposition in liquids. Considering the diffusion and the surface adsorption on the deposit of photochemically produced molecules, we show that the pattern induced (1) is not necessarily an exact replica of the light intensity distribution and (2) can become thick. By implementing experiments with chromate solutions photoactivated by two interfering continuous wave Ar+ laser waves, we validate the model by analyzing the temporal behavior of the first three harmonics of the induced grating.