Interference femtosecond laser stamping of micro-grating structures and time-resolved observation of its dynamics

Selective slicing on a 100 nm thick ZnO film deposited on a Si substrate is achieved by an interference femtosecond (fs) laser stamping. A micro-grating structure with a period of ∼5 μm is completely ablated by an energy-optimized single pulse in one step. The elemental mappings demonstrate complete slice removals of the irradiated areas from the substrate without impurities mixed into the thin film. A calculation of the energy transmitted to the substrate and the characterization of the ablated Si channels infer that the irradiated slices are detached from the substrate by the selective ablation of the thin film and the counterforce of the Si substrate. The temporal and spatial evolution of the grating formation is investigated through a pump-probe microscope using the white light continuum (WLC) as the illumination probe. It is found that the extinctive constructive fringes occur at a delay of 8 picosecond (ps) caused by the increase of electron density. The irradiated slices initially bulge at the delay of 10-12 ps, then subsequently swell until strong material ejections at 800 ps. This study provides an opportunity to advance the understanding of micro-grating fabrications and thin film removals on heterostructures using fs lasers.