Tunable ultrafast control of plasmonic coupling to gold films

We demonstrate ultrafast modulation of the coupling efficiency of free-space radiation to a surface plasmon polariton mode on a gold film with a PMMA grating overlayer over a broad range of wavelengths (540-700 nm). We observe modulation magnitudes of up to 14% at the center of the resonance, or 61% at the outlying regions. The limitations of this method are explored using simulations of the nonequilibrium electron thermal dynamics of the gold and of the response of the grating structure.