This grant provides funding to study a novel dual-pulse laser ablation and plasma amplification (LAPA) process for drilling non-straight microholes with diameters varying arbitrarily with depth. Such kinds of microholes have been increasingly needed by many important applications. However, their precise and efficient drilling still remains a big challenge. The research objectives are to (1) test the hypothesis that in LAPA the amplification of nanosecond-laser-generated plasma by a second picosecond laser pulse can realize controlled and precise material removal from a microhole sidewall through plasma-sidewall interactions and (2) understand the fundamental physics associated with LAPA. The specific research tasks include: (1) Establish an experimental set-up for LAPA. (2) Establish theoretical models for LAPA, which can simulate laser ablation and plasma generation, and laser-plasma-sidewall interactions. (3) Measure the plasma properties to verify the models and understand the fundamental physical processes in LAPA. (4) Perform a feasibility experimental study under the guidance of the verified models. The pump-probe, fast imaging and emission spectroscopy techniques will be used in plasma property measurements. The nonlinear Schrödinger equation and two-temperature hydrodynamic equations will be solved and coupled with a molecular dynamics/Monte Carlo module in modeling the laser-plasma-hole sidewall interactions during LAPA.
LAPA is a novel manufacturing process proposed by the PI. Its essential physical process is the interaction among picosecond laser pulse, plasma (generated by a prior nanosecond laser pulse), and microhole sidewall, which has been rarely studied and is still poorly understood. This project will provide a good, fundamental understanding of this interaction by combining multiscale modeling with comprehensive experiments. The research work will build a solid scientific foundation crucial for LAPA's practical applications. It will also improve our understanding of laser-plasma-material interactions in the general sense, which may improve other existing or inspire new laser and/or plasma-assisted manufacturing processes.
