Laser-induced plasma in aqueous media: numerical simulation and experimental validation of spatial and temporal...

A numerical study of spatial and temporal distribution of a Gaussian-pulsed laser-induced plasma in distilled water is conducted in order to understand the resulting electron density distribution within the plasma plume. The primary motivation behind this study is the recent impetus on laser-induced plasma in the field of microfabrication, where prediction of geometric feature information is paramount to understanding material removal and overall process performance. This simulation predicts the distribution of plasma energy density, absorption coefficient, and laser intensity within the focal region by using a 3D axisymmetric model. The model can be adapted to other nonaqueous condensed media and different laser wavelengths and pulse widths. This numerical model was experimentally validated by an ultrafast gated camera and an external power meter by measuring the plasma energy and residual intensity, respectively. The model and the experimental data show similar qualitative trends in plasma energy density as the beam power is increased. Also the residual intensity data obtained from the model is within 10% of the experimental data for near-threshold intensities and within 40% for super-threshold intensities. The outcomes of this model can be further used as an input for a hydrodynamic model to predict the behavior of the condensed medium or for a thermomechanical model to predict material removal characteristics of the plasma.