Nanoscale acoustic waves detection enhanced by edge plasmon mode resonance in nanoapertures

Abstract

Nanoapertures in metal films confine light to subwavelength dimensions generating enhanced electromagnetic fields. Acoustic resonances of nanostructures can be directly excited by dual frequency lasers due to intensity beating and induce the change of the refractive index in nanoaperture. Here we present that nanoapertures consisting of two intersecting holes support edge plasmons in the form of whispering-gallery modes which are highly sensitive to the refractive index of the surrounding environment. The refractive index variation caused by acoustic resonances in the nanostructure results in a significant change of transmission through the nanoaperture. Experimental results indicate that edge plasmons in the cavity of double nanohole help to minimize radiative losses via stronger confinement and increase acoustic detecting sensitivity. The edge plasmon modes in nanostructures may find applications in nanoparticle trapping, biosensors and light matter interactions in nanofluidics.