Surface Plasmon Interference Device as a Source of Near-Field Power for Photoluminescence

M. Kvapila, b, T. Šikolaa, b, V. Křápeka, b aInstitute of Physical Engineering, Brno University of Technology, Technická 2, 616 69 Brno, Czech Republic bCentral European Institute of Technology, Brno University of Technology, Purkyňova 123, 612 00 Brno, Czech Republic

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We theoretically demonstrate that a simple device consisting of an opaque gold layer with subwavelength slits - the so-called surface plasmon interference device - is capable of transforming the far-field optical power to the near-field one. Optimized slits yield a high conversion efficiency amounting to 45% in terms of the near-field to far-field electric intensity ratio. With a single linear slit arrangement, a propagating wave with a homogeneous field distribution is formed, attributed to surface plasmon polaritons based on its polarization properties. On the other hand, with the slit arrangement supporting interference, it is possible to obtain a standing wave with characteristic spatially modulated interference fringes and spatially separate polarization components. A circular slit can be used for focusing the near-field, with the possibility of obtaining a considerably enhanced field with respect to the excitation. We discuss the implication of the enhanced near-field for the near-field excitation of photoluminescence with the capability to bring a spatial resolution of the photoluminescence spectroscopy beyond the diffraction limit.

DOI:10.12693/APhysPolA.142.668 topics: surface plasmon polariton, near field, photoluminescence