Enhancement of acoustic-wave induced reflection changes through surface plasmon polaritons

We report on enhanced detection of strain waves in gold gratings, using a probe laser pulse tuned at and close to the surface plasmon-polariton (SPP) resonance of the gratings. The enhancement, of up to twenty times, is observed in the strain-wave-induced reaction changes and depends on the type of acoustic wave. For the surface acoustic wave, the enhancement of the optical reaction is greatest at the peak of the resonance, while strain-wave-induced reaction changes of other types of strain waves show their strongest enhancement when the probe pulse is tuned to the wings of the SPP resonance.