Ruthenium under ultrafast laser excitation: Model and dataset for equation of state, conductivity, and electron-ion coupling.

Interaction of ultrashort laser pulses with materials can bring the latter to highly non-equilibrium states, where the electronic temperature strongly differs from the ionic one. The properties of such excited material can be considerably different from those in a hot, but equilibrium state. The reliable modeling of laser-irradiated target requires careful analysis of its properties in both regimes. This paper reports a procedure which provides the equations of state of ruthenium using density functional theory calculations. The obtained data are fitted with analytical functions. The constructed equations of state are applicable in the one- and two-temperature regimes and in a wide range of densities, temperatures and pressures. The electron thermal conductivity and electron-phonon coupling factor are also calculated. The obtained analytical expressions can be used in two-temperature hydrodynamics modeling of Ru targets pumped by ultrashort laser pulses. The data is related to the research article "Similarity in ruthenium damage induced by photons with different energies: From visible light to hard X-rays" [1].

Laser printing of resonant plasmonic nanovoids.

Hollow reduced-symmetry resonant plasmonic nanostructures possess pronounced tunable optical resonances in the UV-vis-IR range, being a promising platform for advanced nanophotonic devices. However, the present fabrication approaches require several consecutive technological steps to produce such nanostructures, making their large-scale fabrication rather time-consuming and expensive. Here, we report on direct single-step fabrication of large-scale arrays of hollow parabolic- and cone-shaped nanovoids in silver and gold thin films, using single-pulse femtosecond nanoablation at high repetition rates. The lateral and vertical size of such nanovoids was found to be laser energy-tunable. Resonant light scattering from individual nanovoids was observed in the visible spectral range, using dark-field confocal microspectroscopy, with the size-dependent resonant peak positions. These colored geometric resonances in far-field scattering were related to excitation and interference of transverse surface plasmon modes in nanovoid shells. Plasmon-mediated electromagnetic field enhancement near the nanovoids was evaluated via finite-difference time-domain calculations for their model shapes simulated by three-dimensional molecular dynamics, and experimentally verified by means of photoluminescence microscopy and Raman spectroscopy.