Controlling surface plasmon polaritons at femtosecond timescales on an aluminum-coated grating

Femtosecond optical control of surface plasmon polaritons (SPPs) has paved an efficient way for the development of high-speed plasmonic switches. However, the mechanism of the ultrafast plasmonic modulation is unclear. Here, using time-resolved optical pump-probe technique, we obtained an ultrafast plasmonic modulation with a sub-100-fs switching time on an aluminum-coated grating in frequency degenerate experiments at the surface plasmon resonance (SPR) condition. We found that the high-speed plasmonic modulation primarily results from the coherent nonlinear interaction of the optical and SPP pulses, combining degenerate measurements at both SPR and non-SPR conditions and non-degenerate experiments. The switching time was measured experimentally with a range of laser pulse widths and estimated theoretically to be eventually limited by the plasmon damping time.