Electron dynamics and prompt ablation of aluminum surface excited by intense femtosecond laser pulse

Ultrafast magnetic light

“…2B), respectively. Such dropping Re(ε) and rising Im(ε) magnitudes are consistent with the increasing intraband contribution at the monotonously rising EHP density, while the following rise represents characteristic red-shift changes of these quantities across absorption bands in strongly photo-excited semiconductors due to their prompt ρ ehdependent bandgap renormalization [35,41,43].Ultrafast photoexcitation of a silicon nanoparticle-The observed large, ultrafast changes of optical dielectric permittivity properties in silicon at fluences below its ablation threshold (for spallation under these experimental conditions, F eff ≈ 0.3 J/cm 2 [45]) can significantly alter optical response of a silicon nanoparticle, supporting a magnetic Mie-type resonance. Basing on the extracted dielectric permittivity values of photoexcited silicon, we study ultrafast dynamics of scattering properties (cross section and diagram) of a silicon nanoparticle near its magnetic resonance by means of full-wave numerical simulations carried out in CST Microwave Studio.…”

“…Simultaneously, ultrafast transient optical modulation for silicon [41,43] and other materials [35] is additionally enhanced due to a strong prompt EHP-driven isotropic renormalization of their direct bandgap, resulting in drastic enhancement of interband transitions and corresponding red spectral shift of the optical dielectric permittivity [35].…”

“…Specifically, an optically driven insulator-conductor transition occurs in such materials, when the fs-laser fluence-dependent EHP frequency passes through the probe frequency, which becomes evident as subsequent reflectivity increase for stronger ionized materials through their intraband electronic transitions [36][37][38]. Simultaneously, ultrafast transient optical modulation for silicon [41,43] and other materials [35] is additionally enhanced due to a strong prompt EHP-driven isotropic renormalization of their direct bandgap, resulting in drastic enhancement of interband transitions and corresponding red spectral shift of the optical dielectric permittivity [35].In this work a realistic dependence of the dielectric permittivity for photo-excited silicon versus incident fslaser fluence at 800-nm laser wavelength was obtained through measurements of single-shot fs-laser pump selfreflectivity (R) from smooth Si surface at its s-(R s (45• )) and p-(R p (45 • )) polarizations at the 45• -incidence angle and variable effective (absorbed) laser fluences where the prompt ρ eh -dependent bandgap shrinkage effect on interband transitions is accounted by the spectral dielectric permittivity dependence with the effective photon frequency ω * = ω + Θρ eh /ρ bgr with the factor Θ, the characteristic renormalization EHP density (ρ bgr ), the characteristic band capacity (ρ bf ) of the specific photo-excited regions of the first Brillouine zone in the k-space, the EHP frequency ω pl and electronic damping time τ e at the pump frequency ω (for details of calculations, see Supplementary materials). The resulting model ρ eh -dependent pump reflectivities R s,p (45…”

“…Specifically, an optically driven insulator-conductor transition occurs in such materials, when the fs-laser fluence-dependent EHP frequency passes through the probe frequency, which becomes evident as subsequent reflectivity increase for stronger ionized materials through their intraband electronic transitions [36][37][38]. Simultaneously, ultrafast transient optical modulation for silicon [41,43] and other materials [35] is additionally enhanced due to a strong prompt EHP-driven isotropic renormalization of their direct bandgap, resulting in drastic enhancement of interband transitions and corresponding red spectral shift of the optical dielectric permittivity [35].…”

“…• , ρ eh ) at the 800-nm pump wavelength were calculated, using a 3 common Fresnel formula and accounting for all basic effects (bandgap renormalization, band filling, EHP screening of the ion core potential [35,43]), fitting well the experimental reflectivity dependences R s,p (45…”