Plasmonic enhancement of mid- and far-infrared acousto-optic interaction [Invited]

We present a concept of an acousto-optical device with plasmonic efficiency enhancement at a 10.6 μm wavelength. Interaction of light, Rayleigh surface acoustic wave, and surface plasmon polariton excited via prism coupling using Otto geometry enhances the diffraction efficiency. In the case of Otto geometry, the surface acoustic wave affects both the refraction index of the optical medium and the air gap thickness between the prism and the metal. Dependencies of the reflective coefficient of the prism–air–metal system on gap thickness and dielectric permittivity modulation were analyzed. The analytical results were confirmed by experimental measurements of the angular spectrum of the reflected beam.