Dionne, J. A. and Sweatlock, L. A. and Atwater, H. A. and Polman, A. (2006) Plasmon slot waveguides: Towards chip-scale propagation with subwavelength-scale localization. Physical Review B, 73 (3). Art. No. 035407. ISSN 1098-0121 http://resolver.caltech.edu/CaltechAUTHORS:DIOprb06
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We present a numerical analysis of surface plasmon waveguides exhibiting both long-range propagation and spatial confinement of light with lateral dimensions of less than 10% of the free-space wavelength. Attention is given to characterizing the dispersion relations, wavelength-dependent propagation, and energy density decay in two-dimensional Ag/SiO2/Ag structures with waveguide thicknesses ranging from 12 nm to 250 nm. As in conventional planar insulator-metal-insulator (IMI) surface plasmon waveguides, analytic dispersion results indicate a splitting of plasmon modes—corresponding to symmetric and antisymmetric electric field distributions—as SiO2 core thickness is decreased below 100 nm. However, unlike IMI structures, surface plasmon momentum of the symmetric mode does not always exceed photon momentum, with thicker films (d~50 nm) achieving effective indices as low as n=0.15. In addition, antisymmetric mode dispersion exhibits a cutoff for films thinner than d=20 nm, terminating at least 0.25 eV below resonance. From visible to near infrared wavelengths, plasmon propagation exceeds tens of microns with fields confined to within 20 nm of the structure. As the SiO2 core thickness is increased, propagation distances also increase with localization remaining constant. Conventional waveguiding modes of the structure are not observed until the core thickness approaches 100 nm. At such thicknesses, both transverse magnetic and transverse electric modes can be observed. Interestingly, for nonpropagating modes (i.e., modes where propagation does not exceed the micron scale), considerable field enhancement in the waveguide core is observed, rivaling the intensities reported in resonantly excited metallic nanoparticle waveguides.
|Additional Information:||©2006 The American Physical Society (Received 9 July 2005; revised 2 November 2005; published 5 January 2006) The authors would like to thank Henri Lezec and Domenico Pacifici for thoughtful and engaging discussions related to this work. Financial support at Caltech was provided by the Air Force Office of Scientific Research, MURI Grant No. FA9550-04-1-0434. One of us (J.A.D.) acknowledges fellowship support from the National Science Foundation and the Department of Defense Army Research Office. Work at AMOLF is part of the research program of FOM and is financially supported by NWO.|
|Subject Keywords:||silver; silicon compounds; surface plasmons; visible spectra; infrared spectra; light propagation; optical waveguide theory|
|Usage Policy:||No commercial reproduction, distribution, display or performance rights in this work are provided.|
|Deposited By:||Archive Administrator|
|Deposited On:||31 Mar 2006|
|Last Modified:||26 Dec 2012 08:48|
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