Study on the mechanism of a femtosecond laser-induced breakdown of the deposited substrate mediated by aluminum nanoparticles in a vacuum

The mechanism of a femtosecond laser-induced breakdown of deposited substrates mediated by aluminum nanoparticles in a vacuum environment was studied. This model of optical breakdown mediated by aluminum nanoparticles includes the electromagnetic field model for the description of near-field enhancement of aluminum nanoparticles, the two-temperature model for the description of electron and lattice temperature of aluminum nanoparticles, and the plasma model for the description of the evolution of electron density in the deposited substrate. These three physical field models were fully coupled in this model. We defined a new modified dielectric function model to describe the dielectric function of aluminum nanoparticles, due to the strength of near-field enhancement depends on the size and morphology of nanoparticles. The near-field enhancement of different types of aluminum nanoparticles, the femtosecond laser breakdown threshold of deposited substrates, and the evolution of the lattice temperature of aluminum nanoparticles were investigated. The results showed that assembled aluminum nanoparticles can significantly reduce the femtosecond laser breakdown threshold of deposited substrates in a vacuum, and the lattice temperature of aluminum nanoparticle was lower than the melting point, under the irradiation of a single-pulse femtosecond laser with a wavelength of 800 nm and pulse width of 25 fs.