  The employment of femtosecond pulsed lasers has received significant
attention due to its capability to facilitate fabrication of precise patterns
at the micro- and nano- lengths scales. A key issue for efficient material
processing is the accurate determination of the damage threshold that is
associated with the laser peak fluence at which minimal damage occurs on the
surface of the irradiated solid. Despite a wealth of previous reports that
focused on the evaluation of the laser conditions that lead to the onset of
damage, the investigation of both the optical and thermal response of thin
films of sizes comparable to the optical penetration depth is still an
unexplored area. In this report, a detailed theoretical analysis of the impact
of various parameters such as the photon energies and material thickness on the
damage threshold for various metals (Au, Ag, Cu, Al, Ni, Ti, Cr, Stainless
Steel) is investigated. A multiscale physical model is used that correlates the
energy absorption, electron excitation, relaxation processes and minimal
surface modification which leads to the onset of material damage. The
satisfactory agreement of the theoretical model with some experimental results
indicates that the damage threshold evaluation method could represent a
systematic approach towards designing efficient laser-based fabrication systems
and optimizing the processing outcome for various applications.
