Interband and intraband (Drude) contributions to femtosecond laser absorption in aluminum.

摘要: Theoretical and experimental investigations of the absorption in metallic aluminum femtosecond-laser radiation pulses with peak intensity ${I}_{0}\ensuremath{\lesssim}{10}^{15} {\mathrm{W}/\mathrm{c}\mathrm{m}}^{2}$ are reported. Energy balance equations solved for electron phonon subsystems, together Helmholtz equation laser radiation. Expressions relaxation times as functions temperatures obtained, no free parameters. Contrary to assumption made published studies, we find that interband rather than intraband (Drude) plays dominant role near infrared throughout visible region at low moderate intensities. For 50 fs, 800 nm transitions dominates intensities up few ${10}^{13} {\mathrm{W}/\mathrm{c}\mathrm{m}}^{2}.$ such pulses, broadening parallel-band line increase results, ${I}_{0}l~5\ifmmode\times\else\texttimes\fi{}{10}^{13} {\mathrm{W}/\mathrm{c}\mathrm{m}}^{2},$ decrease coefficient compared room-temperature value. In this paper, present both first theoretical prediction observation phenomenon. Dielectric permittivity gradients within skin layer also contribute absorption. The mechanisms lattice disordering considered quantitatively, it is shown ${I}_{0}l{10}^{14} melting does not occur laser-pulse duration. Experimental results presented 400 wavelengths. agreement between theory experiment very good.