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Polarization-Controlled Tunable Directional Coupling of Surface Plasmon Polaritons

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Science  19 Apr 2013:
Vol. 340, Issue 6130, pp. 331-334
DOI: 10.1126/science.1233746

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Controlling Light Propagation

Surface plasmons are light-induced collective electronic excitations in a metal that offer the possibility of manufacturing optoelectronic devices at nanometer scale. Before such shrinking can be achieved, the propagation direction and lifetime of the plasmonic excitations have to be controlled (see the Perspective by Miroshnichenko and Kivshar). Rodríguez-Fortuño et al. (p. 328) show how this is done using polarized light. Alternatively, using an array of metallic nanoantennae (in this case, slits) patterned into a thin gold film, Lin et al. (p. 331) present a further improvement on current plasmonic coupling schemes that has the potential to encode information contained in both the intensity and polarization of light.

Abstract

Light can be coupled into propagating electromagnetic surface waves at a metal-dielectric interface known as surface plasmon polaritons (SPPs). This process has traditionally faced challenges in the polarization sensitivity of the coupling efficiency and in controlling the directionality of the SPPs. We designed and demonstrated plasmonic couplers that overcome these limits using polarization-sensitive apertures in a gold film. Our devices enable polarization-controlled tunable directional coupling with polarization-invariant total conversion efficiency and preserve the incident polarization information. Both bidirectional and unidirectional launching of SPPs are demonstrated. The design is further applied to circular structures that create radially convergent and divergent SPPs, illustrating that this concept can be extended to a broad range of applications.

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