Abstract
We show that the interaction between localized surface plasmons sustained by a metallic nano-antenna and delocalized phonons lying at the surface of an heteropolar semiconductor can generate a new class of hybrid electromagnetic modes. These plasphonic modes are investigated using an analytical model completed by accurate Green dyadic numerical simulations. When surface plasmon and surface phonon frequencies match, the optical resonances exhibit a large Rabi splitting typical of strongly interacting two-level systems. Based on numerical simulations of the electric near-field maps, we investigate the nature of the plaphonic excitations. In particular, we point out a strong local field enhancement boosted by the phononic surface. This effect is interpreted in terms of light harvesting by the plasmonic antenna from the phononic surface. We thus introduce the concept of active phononic surfaces that may be exploited for far-infared optoelectronic devices and sensors.
Highlights
Over the last twenty years, a considerable amount of original nano–photonic developments were based on the mastering of the physics of surface plasmons
Preliminary theoretical studies have highlighted the strong concentration of infrared energy that are produced by the synergistic interaction of surface plasmons and surface phonons [18]
The Rabi splitting is clearly due to the interaction between the dipole antenna and the surface phonons and is proportional to the LO-TO splitting δ, i.e. to the square root of the electromagnetic field generated by the surface phonons
Summary
Over the last twenty years, a considerable amount of original nano–photonic developments were based on the mastering of the physics of surface plasmons. In the case of polar semiconductors, this occurs in the Reststrahllen band, i.e. between the transverse and the longitudinal optical phonon frequencies In this frequency gap, the atomic vibrations generate electromagnetic fields that propagate along the surface with a strong localization in the perpendicular direction. Huber et al [17] have demonstrated the generation and focusing of surface phonon– polaritons at the surface of a SiC crystal by using elongated metal nanostructures Following these experiments, preliminary theoretical studies have highlighted the strong concentration of infrared energy that are produced by the synergistic interaction of surface plasmons and surface phonons [18]. The analytical results are completed by realistic Green dyadic numerical simulations of the optical resonances and the corresponding electric near–field maps
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