Abstract

The understanding of the energy deposition dynamics of femtosecond pulses propagating in dielectric media is a key ingredient for the optimization of laser machining processes [1]. Usually, spatially resolved energy density maps are retrieved from postmortem inspection of solid materials [2], a method which is not suitable for liquids. In this context, we have developed a new method for measuring the energy content of light wave-packets as they propagate in homogeneous Raman-active liquids or solids. To test the method, we spatially resolved the energy deposition dynamics of a 810 nJ, 120 fs, λ=800 nm pump pulse, tightly focused in water. The comparison between the energy losses, measurements of the plasma density, and the outcomes of a realistic numerical model of the experiment allowed us to clearly show that the ionization threshold of water is 8 eV, rather than the commonly used value of 6.5 eV [3].

© 2015 IEEE