Ultrasmooth metallic films with buried nanostructures for backside reflection-mode plasmonic biosensing

Authors

  • N.C. Lindquist,

    1. Laboratory of Nanostructures and Biosensing, Department of Electrical and Computer Engineering, University of Minnesota, Minneapolis, MN 55455 USA
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    • Current address: Physics Department, Bethel University, St. Paul, MN 55112, USA

    • These authors contributed equally to this work.

  • T.W. Johnson,

    1. Laboratory of Nanostructures and Biosensing, Department of Electrical and Computer Engineering, University of Minnesota, Minneapolis, MN 55455 USA
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    • These authors contributed equally to this work.

  • J. Jose,

    1. Laboratory of Nanostructures and Biosensing, Department of Electrical and Computer Engineering, University of Minnesota, Minneapolis, MN 55455 USA
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  • L.M. Otto,

    1. Laboratory of Nanostructures and Biosensing, Department of Electrical and Computer Engineering, University of Minnesota, Minneapolis, MN 55455 USA
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  • S.-H. Oh

    Corresponding author
    1. Laboratory of Nanostructures and Biosensing, Department of Electrical and Computer Engineering, University of Minnesota, Minneapolis, MN 55455 USA
    2. Department of Biophysics and Chemical Biology, Seoul National University, Seoul, 151-747, Korea
    • Laboratory of Nanostructures and Biosensing, Department of Electrical and Computer Engineering, University of Minnesota, Minneapolis, MN 55455 USA
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    • phone: +1 612 625 0125


Abstract

A new plasmonic device architecture based on ultrasmooth metallic surfaces with buried plasmonic nanostructures is presented. Using template-stripping techniques, ultrathin gold films with less than 5 Å surface roughness are optically coupled to an arbitrary arrangement of buried metallic gratings, rings, and nanodots. As a prototypical example, linear plasmonic gratings buried under an ultrasmooth 20 nm thick gold surface for biosensing are presented. The optical illumination and collection are completely decoupled from the microfluidic delivery of liquid samples due to the backside, reflection-mode geometry. This allows for sensing with opaque or highly scattering liquids. With the buried nanostructure design, high sensitivity and decoupled backside (reflective) optical access are maintained, as with traditional prism-based surface plasmon resonance (SPR) sensors. In addition, the benefits offered by nanoplasmonic sensors such as spectral tunability and high-resolution, wide-field SPR imaging with normal-incidence epi-illumination that is simple to construct and align are gained as well. Beyond sensing, the buried plasmonic nanostructures with ultrasmooth metallic surfaces can benefit nanophotonic waveguides, surface-enhanced spectroscopy, nanolithography, and optical trapping.

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