Nanofocusing in laterally tapered plasmonic waveguides. Opt Express

Center for Nanophotonics, FOM-Institute for Atomic and Molecular Physics (AMOLF), Kruislaan 407, 1098 SJ Amsterdam, The Netherlands.
Optics Express (Impact Factor: 3.49). 01/2008; 16(1):45-57. DOI: 10.1364/OE.16.000045
Source: PubMed


We investigate the focusing of surface plasmon polaritons (SPPs) excited with 1.5 microm light in a tapered Au waveguide on a planar dielectric substrate by experiments and simulations. We find that nanofocusing can be obtained when the asymmetric bound mode at the substrate side of the metal film is excited. The propagation and concentration of this mode to the tip is demonstrated. No sign of a cutoff waveguide width is observed as the SPPs propagate along the tapered waveguide. Simulations show that such concentrating behavior is not possible for excitation of the mode at the low-index side of the film. The mode that enables the focusing exhibits a strong resemblance to the asymmetric mode responsible for focusing in conical waveguides. This work demonstrates a practical implementation of plasmonic nanofocusing on a planar substrate.

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Available from: Laurens Kuipers, Jan 28, 2014
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    • "Previously, to launch surface plasmons towards a sharp gold tip, gratings have been milled into the side of an electrochemically etched gold wire13. Likewise, the use of nanohole gratings next to a region with a laterally tapered thin gold film have also been demonstrated14. In a different scheme, curved slits262728 or holes29 focus plasmons to an in-plane bright spot. "
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    ABSTRACT: We demonstrate the design, fabrication and characterization of a near-field plasmonic nanofocusing probe with a hybrid tip-plus-aperture design. By combining template stripping with focused ion beam lithography, a variety of aperture-based near-field probes can be fabricated with high optical performance. In particular, the combination of large transmission through a C-shaped aperture aligned to the sharp apex (<10 nm radius) of a template-stripped metallic pyramid allows the efficient delivery of light-via the C-shaped aperture-while providing a nanometric hotspot determined by the sharpness of the tip itself.
    Scientific Reports 05/2013; 3:1857. DOI:10.1038/srep01857 · 5.58 Impact Factor
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    • "The most intuitive approach consists of introducing geometrical boundaries by patterning the metal layer. This has for instance enabled subwavelength guiding of SPPs along strips [4] [5] , V-grooves and slots [6 – 8] as well as adiabatic focusing [9] [10] . "
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    ABSTRACT: Surface plasmons polaritons (SPPs) at metal/dielectric interfaces have raised lots of expectations in the on-going quest towards scaling down optical devices. SPP optics offers a powerful and flexible platform for real two-dimensional integrated optics, capable of supporting both light and electrons. Yet, a full exploitation of the features of SPPs is conditioned by an accurate control of their flow. Most efforts have so far focused on the extrapolation of concepts borrowed from guided optics. This strategy has already led to many important breakthroughs but a fully deterministic control of SPP modes remains a challenge. Recently, the field of optics was stimulated by a novel paradigm, transformation optics, which offers the capability to control light flow in any desired fashion. While it has already significantly contributed to the design of metamaterials with unprecedented optical properties, its versatility offers new opportunities towards a fully deterministic control of SPPs and the design of a new class of plasmonic functionalities. Here, we review recent progress in the application of transformation optics to SPPs. We first briefly describe the theoretical formalism of transformation plasmonics, focusing on its specificities over its three-dimensional optical counterpart. Numerical simulations are then used to illustrate its capability to tame SPP flows at a metal interface patterned with a dielectric load. Finally, we review recent experimental implementations leading to unique SPP functionalities at optical frequencies.
    07/2012; 1(1-1):51-64. DOI:10.1515/nanoph-2012-0011
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    ABSTRACT: Three types of indirect phase tuning-based plasmonic structures with subwavelength circular grooves/slits and/or central apertures corrugated on Au film supported by glass substrate: depth modulation, width modulation, and hybrid depth-width modulation, were put forth in this paper. They were investigated experimentally by means of nanofabrication and near-filed scanning optical microscope characterization. The plasmonic structures were fabricated using the technique of focused ion beam direct milling. Our experimental results demonstrated that all of the phase tuning-based structures have focusing functions. Both the width and depth modulation-based structures can realize beam focusing and produce an elongated depth of focus. Moreover, after comparison among these three structures, we found that the width modulation-based structure has the best focusing performance. KeywordsPlasmonic structures–NSOM–FIB–Indirect phase modulation
    Plasmonics 06/2011; 6(2):227-233. DOI:10.1007/s11468-010-9192-1 · 2.24 Impact Factor
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