Ultrafast Laser Ablation of Solid Targets: A Versatile Method for Fast Ion Generation and Nanoparticle Synthesis

Ultrashort laser ablation (ULA) has opened up a wide range of new applications in industry, material science, and medicine. This chapter summarizes the different aspects of ultrashort laser (800nm, 50fs, Ti: Sapphire) ablation of solid targets (copper and silicon). In particular, we will focus on ULA of metals, namely emphasizing on the results obtained by the authors. The spatial and temporal evolution of ultrafast laser produced plume components, in high vacuum conditions, is studied through a spectrally resolved imaging technique. The ionic (Cu+) and neutrals (Cu*) components are separately imaged by introducing corresponding bandpass interference filters in front of a fast gated intensified charge coupled device (ICCD), while nanoparticles are investigated by imaging their characteristic broadband emission [3]. Since each image is a representative of particular plume component; this analysis gives more insights into the fundamentals of ULA and its possible applications. The presence of fast ion components and significant production of nanoparticle are observed in the investigated laser intensity regime 3×1013 - 3×1014 W/cm2.The ionic components in the laser-produced plume (LPP) are studied using a negatively biased Langmuir probe; which gives the angular distribution and average kinetic energy of ions produced during ULA. The obtained results are consistent with the outcomes of spectrally resolved imaging technique. The angular distribution of the ion flux is well-described by an adiabatic and isentropic expansion model of a plume produced by solid-target laser ablation (LA). Femtosecond laser ablation from solid targets has shown its capability in producing nanoparticles of different materials, even in high vacuum conditions. In our experimental conditions of ultrashort laser ablation, the kinetic energy of the fastest ejected species can be increased up to a few keV leading to a better adhesion of the film on various substrates. Preliminary results on similar experiments using a silicon target are also discussed compared.