Ultrafast dynamics of the real and imaginary permittivity parts of a photoexcited silver layer revealed by surface plasmon resonance

摘要

Dynamics of the real and imaginary parts of the dielectric permittivity of a photoexcited silver layer has been investigated by means of femtosecond pump-probe spectroscopy in a surface plasmon resonance Kretschmann configuration. Both real and imaginary permittivity parts experience changes in the visible-near-IR regions under silver excitation at 400 nm. The changes are stronger, particularly those of the imaginary part, at longer wavelengths. Three excited states are formed during the relaxation process, which are attributed to the nonequilibrium and equilibrium heated electron distributions and lattice heating. Different time evolutions of the real and imaginary dielectric permittivity parts are explained by different contributions from interband and intraband transitions caused by plasma frequency and electron scattering frequency variations. (c) 2008 Optical Society of America.