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Université Jean Monnet – Saint-Etienne |  |
Journal articles
Ultrafast switching of surface plasmonic conditions in nonplasmonic metals
Abstract : We demonstrate that ultrafast carrier excitation can drastically affect electronic structures in nonplasmonic metals and determine a transient, brief surface plasmonic state, potentially creating the conditions for a plasmonic switch. The initial state can be related to d-band partial filling and splitting, with a pseudo-band-gap accommodating the chemical potential. This determines a quasi-resonant-like spectral behavior of the optical constants for pumping carriers across the d-band pseudogap, i.e., visible frequencies. The relation between real and imaginary parts of the refractive index does not fulfill surface plasmonic conditions in the visible photon range. Using first-principles molecular dynamics and Kubo-Greenwood formalism for laser-excited tungsten we show that carrier heating mobilizes d electrons into collective inter-and intraband transitions leading to a sign flip in the imaginary optical conductivity, activating plasmonic properties for the initial nonplasmonic phase. The drive for the laser-induced optical evolution in this case does not rely on a variation of the free electron number but can be visualized as an increasingly damped character of the quasiresonance at visible frequencies. Here laser heating determines an energy-dependent degree of occupation with broadening profiles. The subsequent evolution of optical indices for the excited material is confirmed by time-resolved ultrafast ellipsometry. The large optical tunability extends the existence spectral domain of surface plasmons in ranges typically claimed in laser self-organized nanostructuring. Nonequilibrium heating is thus a strong factor for engineering optical control of evanescent excitation waves, particularly important in laser nanostructuring strategies.
Cited literature [36 references]
https://hal-ujm.archives-ouvertes.fr/ujm-01340983
Contributor : Jean-Philippe Colombier Connect in order to contact the contributor
Submitted on : Sunday, July 3, 2016 - 1:41:59 PM
Last modification on : Monday, June 14, 2021 - 10:03:25 AM
Long-term archiving on: : Tuesday, October 4, 2016 - 10:55:13 AM
Contributor : Jean-Philippe Colombier Connect in order to contact the contributor
Submitted on : Sunday, July 3, 2016 - 1:41:59 PM
Last modification on : Monday, June 14, 2021 - 10:03:25 AM
Long-term archiving on: : Tuesday, October 4, 2016 - 10:55:13 AM
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