Abstract
Evaluating the optical properties of matter under the action of ultrafast light is crucial in modeling laser–surface interaction and interpreting laser processing experiments. We report optimized coefficients for the Drude-Lorentz model describing the permittivity of several transition metals (Cr, W, Ti, Fe, Au, and Ni) under electron-phonon nonequilibrium, with electrons heated up to 30,000 K and the lattice staying cold at 300 K. A Basin-hopping algorithm is used to fit the Drude-Lorentz model to the nonequilibrium permittivity calculated using ab initio methods. The fitting coefficients are provided and can be easily inserted into any calculation requiring the optical response of the metals during ultrafast irradiation. Moreover, our results shed light on the electronic structure modifications and the relative contributions of intraband and interband optical transitions at high electron temperatures corresponding to the laser excitation fluence used for surface nanostructuring.
Highlights
IntroductionIntense photoexcitation in the femtosecond range for fluence near the ablation threshold, typically 0.2 J/cm for most of transition metals, forces conduction electrons in metals to move around the lattice ions, enabling photon absorption through an inverse bremsstrahlung process [1]
Contrary to simple metals, such as Al, Mg, or Zn, transition metals are characterized by the presence of d-bands that translate into a high-density d-block in the density of states (DOS) [5]
A Drude-Lorentz model coefficients describing the permittivity dispersion of laser-excited transition metals are proposed
Summary
Intense photoexcitation in the femtosecond range for fluence near the ablation threshold, typically 0.2 J/cm for most of transition metals, forces conduction electrons in metals to move around the lattice ions, enabling photon absorption through an inverse bremsstrahlung process [1]. Throughout the laser-solid absorption, the electrons are redistributed within the density of states respecting the Pauli exclusion principle. This involves intraband and interband displacements of the electron population, followed by thermalization within the bands [4]. Tractable models and simulation approaches capable of describing fast electron dynamics are formulated
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
