Femtosecond pulse laser-induced self-organized microstructure on europium complex film

A high repetition rate femtosecond laser was used to irradiate a europium complex film, and a self-organizing symmetrical structure-like droplet was successfully induced which we called micro-crown structure. In order to research the relationship between micro-crown formation and machining condition, we changed laser pulses, average power, and numerical aperture of microscope. We analyzed the experiment results theoretically by referring to laser molten pool model and droplets sputtering model. The micro-crown structure appeared in femtosecond laser irradiation region while the pulses reached a certain value. Irradiation region size change was caused by thermo-capillary forces and chemical-capillary forces in liquid area. The sputter change was due to rapid gas expansion in gaseity area caused by multiphoton absorption.