Abstract: Laser-induced breakdown plays a crucial role in laser applications. Consequently, investigating the influence of different parameters is important for improving and optimizing laser-based applications. This work examines the wavelength dependence of breakdown in air using a model that couples a free-electron rate equation with a two-temperature plasma description. The model includes multiphoton and avalanche ionization as the main electron generation processes, as well as recombination, attachment, diffusion, and inverse bremsstrahlung absorption, which are responsible for electron losses from the volume. Numerical results are obtained for two representative wavelengths, $$λ=355nm$$ and $$λ=532nm$$, under comparable pulse and focusing conditions. We show that plasma formation at shorter wavelengths is more efficiently initiated through multiphoton ionization, whereas at higher wavelengths, stronger inverse bremsstrahlung heating enhances avalanche ionization, resulting in higher electron densities and more pronounced plasma development.

Keywords: laser-matter interaction, laser-induced breakdown, two-temperature model, free-electron density, plasma formation, wavelength dependence, ultrashort laser pulses

Pages: 58-65