Resonance excitation of polaritons and plasmons at the interface between a uniaxial crystal and a metal |
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Authors: | V I Alshits and V N Lyubimov |
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Institution: | (1) University of Arizona, Tucson, AZ, USA; |
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Abstract: | A resonance is theoretically predicted in which a plane electromagnetic wave in a transparent optically uniaxial crystal,
reflected from its metallized surface, creates a wave field at the interface whose intensity is considerably higher than the
intensity of the incident wave. In the crystal, a high-intensity (bulk or surface) polariton is excited, whereas, in the metal,
a large-amplitude localized plasmon is excited. The structure of the fields created in the crystal is close to that of the
fields of bulk polaritons at the boundary with a perfectly conducting surface. The nonideality of the metal is taken into
account in the Leontovich impedance approximation. Conditions are found under which the resonance is accompanied by a full
transformation of the incident wave into a polariton-plasmon localized near the interface. This coupled wave can be considered
as a pumped eigenmode. The intensity of the wave field localized at the boundary can amount to 10–15 times the intensity of
the incident wave in the visible range. The resonance half-width with respect to the angles of incidence amounts to a few
degrees. In the infrared range, the excitation factor can be an order of magnitude higher, while the resonance half-width
sharply decreases down to about 0.1° for a wavelength of 5 μm. Conditions are obtained for the resonance excitation of high-intensity
bulk polaritons that arise as reflected modes propagating at a small angle to the boundary. The phenomena investigated are
completely attributed to the anisotropy of the crystal. |
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