title: Ultrafast Nonlinear Response of Bulk Plasmons in Highly Doped ZnO Layers.
abstract: Longitudinal bulk plasmons in an n-doped ZnO layer system are studied by two-color femtosecond pump-probe spectroscopy in the midinfrared. The optical bulk plasmon resonance identified in linear reflectivity spectra undergoes a strong redshift and a limited broadening upon intraband excitation of electrons. The nonlinear changes of plasmon absorption decay on a time scale of 2 ps and originate from the intraband redistribution of electrons. Theoretical calculations explain the plasmon redshift by the transient increase of the ensemble-averaged electron mass and the concomitantly reduced plasma frequency in the hot electron plasma. The observed bulk plasmon nonlinearity holds strong potential for applications in plasmonics.
authors.affiliation: Max-Born-Institut für Nichtlineare Optik und Kurzzeitspektroskopie, D-12489 Berlin, Germany.
authors.forename: Tobias
authors.initials: T
authors.lastname: Tyborski
authors.affiliation: Institut für Physik, Humboldt-Universität zu Berlin, D-12489 Berlin, Germany.
authors.forename: Sascha
authors.initials: S
authors.lastname: Kalusniak
authors.affiliation: Institut für Physik, Humboldt-Universität zu Berlin, D-12489 Berlin, Germany.
authors.forename: Sergey
authors.initials: S
authors.lastname: Sadofev
authors.affiliation: Institut für Physik, Humboldt-Universität zu Berlin, D-12489 Berlin, Germany.
authors.forename: Fritz
authors.initials: F
authors.lastname: Henneberger
authors.affiliation: Max-Born-Institut für Nichtlineare Optik und Kurzzeitspektroskopie, D-12489 Berlin, Germany.
authors.forename: Michael
authors.initials: M
authors.lastname: Woerner
authors.affiliation: Max-Born-Institut für Nichtlineare Optik und Kurzzeitspektroskopie, D-12489 Berlin, Germany.
authors.forename: Thomas
authors.initials: T
authors.lastname: Elsaesser