  We demonstrate that the dispersion of surface plasmon polaritons in a
periodically perforated gold film can be efficiently manipulated by femtosecond
laser pulses with the wavelengths far from the intrinsic resonances of gold.
Using a time- and frequency- resolved pump-probe technique we observe shifting
of the plasmon polariton resonances with response times from 200 to 800 fs
depending on the probe photon energy, through which we obtain comprehensive
insight into the electron dynamics in gold. We show that Wood anomalies in the
optical spectra provide pronounced resonances in differential transmission and
reflection with magnitudes up to 3% for moderate pump fluences of 0.5 mJ/cm^2.
