Abstract
Excitation using femtosecond laser pulses induced ultrafast heating of discontinuous gold nanowires, resulting in transient thermal expansion of the gold nanostructures that constitute the nanowires. The cross-plasmon resulting from the closely arranged gold nanostructures along the nanowires was modified by the change in the small gaps due to the thermal effect. This led to the spectral shift of the cross-plasmon resonance and laid the photophysical basis for the optical switching. A femtosecond pump-probe scheme was used to investigate the ultrafast optical switching dynamics. The most efficient optical switching effect was observed when the pump and probe laser pulses were polarized perpendicular and parallel to the discontinuous gold nanowires, respectively.
Highlights
Plasmonic optical switching effects have been reported on extensively, and are based on the spectral shift of the localized surface plasmon resonance (LSPR) of the metallic nanostructures [1,2,3,4].Modification on the electron–electron and electron–phonon scattering processes by the intensive ultrashort laser pulses has been the main physical mechanism [5,6,7]
1.8 to μJ/cm a function of the pump fluence increased from 1.8 to 23.1 μJ/cm2; (c) Rebuilt optical extinction spectra spectra with the transient absorption (TA) spectra included for transverse electric (TE) polarization at different pump with the transient absorption (TA) spectra included for TE polarization at different pump fluence, fluence, showing the red-shift of plasmon resonance with increasing pump fluence
Cross-plasmons that are dependent on the gap widths
Summary
Plasmonic optical switching effects have been reported on extensively, and are based on the spectral shift of the localized surface plasmon resonance (LSPR) of the metallic nanostructures [1,2,3,4]. A cross-plasmon has been demonstrated in the three-dimensional (3D) network of gold nanowires, where Fano coupling between Rayleigh anomaly and such cross-plasmon provides us new opportunities to achieve efficient optical switching devices [14] Such cross-plasmons can be achieved very commonly in metallic nanostructures with very small separation gaps, which depend strongly on the gap width and on the polarization direction of the light. We investigate the polarization-dependent optical switching effects in a waveguide-gold-nanowire grating. The localized surface plasmons resonant at these gaps may be be modified byby optical pulses. The localized surface plasmons resonant at these gaps may modified optical This is the basic for the for polarization-dependent optical switching described in pulses. Previous publication [1,14]
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