PNNL

Abstract

This study investigates the role of laser excitation wavelength on early time dynamics of laser-produced plasma (LPP). The LPP was generated by focusing fundamental (1064 nm), second (532 nm), and fourth (266 nm) harmonic radiation from a 6 ns Nd:YAG laser at a laser intensity of 10 GWcm-2 onto a copper target. The early time evolution of the plasma was then analyzed using Nomarski interferometry, allowing for the determination of plasma properties such as electron density distribution, plume velocity, and morphology. The plasma properties obtained using Nomarski interferometry were then correlated to emission measurements obtained using fast-gated imaging. Results show that the plume size and morphology change significantly with wavelength, whereas the average electron density has a much weaker dependence. Comparisons of plume morphology between interferograms and self-emission images are shown to be highly consistent, and the variation in emission intensity is shown to be directly related to the evolution of the plasma density