Hybrid-Mode-Assisted Long-Distance Excitation of Short-Range Surface Plasmons in a Nanotip-Enhanced Step-Index Fiber

Significance Statement

Surface plasmon polaritons have recently been found useful in applications that require strong field enhancement on nanoscale spots. These applications include nonlinear plasmonics, near field microscopy, bio-sensing photovoltaics, field-enhanced microscopy and quantum plasmonics. The wide range of applications has mainly been driven by the rapid progress in nanofabrications and design capabilities. However, challenges have emerged when it comes to the delivery efficiency and light collection on the nanoscale, especially on an integrated optical fiber platform. The available near field optical microscopy techniques majorly depend on cantilevers and subwavelength aperture based probes and become inefficient when the aperture size falls below a given range.

A research team led by professor Markus Schmidt at the Leibniz Institute of Photonic Technology in Germany developed a fully integrated fiber-based near-field nanoprobe for the broadband delivery of light to nanoscale dimensions using short-range surface plasmon polaritons on a metallic nanotip, having an apex size less than 10 nm, which would provide a new nanophotonic platform with the potential to break the current limits of near field microscopy. They aimed at developing a monolithic nanowire-enhanced fiber-based nanoprobe for the broadband delivery of light (550−730 nm) to a deep subwavelength scale by using short-range surface plasmons. The research work is now published in Nano Letters.

First, they formed the geometry by using a step index fiber with an integrated gold nanowire in its core and a protruding gold nanotip with sub-apex radius of 10 nm. The researchers then presented a new coupling scheme to excite short-range surface plasmons on a gold nanowire through a cylindrical polarized hybrid dielectric mode. The radially polarized hybrid mode propagated inside the nanowire section and was used to excite the plasmonic mode at the fiber end face. This in turn super focused down to nanoscale dimensions at the tip apex.

The researchers observed that in this plasmonic coupling scheme, the wire length could be orders of magnitude longer than the attenuation length of short-range plasmon polaritons, which reduces demands in fabrication. The broadband scattered light in the far field from the nanotip due to plasmonic excitation was observed to be axially polarized and preferentially excited by a radially polarized input, revealing that it originated from a short range plasmon propagating on the nanotip.

The short-range surface plasmon polaritons’ unique property of being able to nanofocus on a mechanically flexible and monolithic fiber platform will enable the nanoprobe to be applied in a wide range of applications. The researchers are highly optimistic that such nanoprobes will offer significant improvement in both spatial resolution and delivery efficiencies, when compared to currently used near-field tips.

Hybrid-Mode-Assisted Long-Distance Excitation of Short-Range Surface Plasmons in a Nanotip-Enhanced Step-Index Fiber-advances in engineering

About The Author

Alessandro Tuniz is a University of Sydney Postdoctoral Fellow be at the Australian Institute for Nanoscience and Technology starting in June 2017. In 2014 he received a Humboldt Postdoctoral Fellowship to work at the Leibniz Institute of Photonic Technology in Jena on the topic of fibre-plasmonics, with the aim of integrating novel active and passive functionalities into optical fibers on the basis of metallic nanowires. In 2009 he helped launch as a doctoral student the metamaterial fibers group, completeing his PhD in 2013 on the topic of fiber-based terahertz metamaterials for deeply sub-wavelength imaging. He received the B.Sc. degree in Physics from The University of Trieste (Italy) in 2007, and the B.Sc. (Honours) at the University of Sydney in 2008.

His research interests center on plasmonics, metamaterials, sub-wavelength imaging, and nonlinear optics in the context of optical fibers and hybrid (multi-material) structures, including both experimental and numerical simulation techniques.

About The Author

Since November 2012 Markus A. Schmidt owns a full professorship for fiber optics at the Friedrich-Schiller University Jena (Germany) and is head of a newly established research group at the Institute for Photonic Technologies (IPHT). His main research topic is combining optical fiber technology with nanophotonic concepts for implementing devices with applications in areas such as biophotonics, plasmonics or nonlinear optics.

From 2006 to 2012 he was leader of the group “nanowire” in the division of Philip Russell at the Max Planck Institute for the Science of Light in Erlangen (Germany). His main research topic was nanowires inside optical fiber with applications in areas such as nonlinear optics, plasmonics, opto-fluidics, material science, optical detector, fiber polarizers, band gap structures and biophysics. Between April 2011 and March 2012 Markus Schmidt spend a twelve months research leave at the Centre of Plasmonics and Metamaterials at Imperial College London (UK), working on magnetoplasmonics and hybrid photonic-plasmonic systems. He finished his postdoctoral lecture degree (Habilitation) at the University Erlangen-Nuremberg in June 2012. He obtained his Dr. rer. nat. degree (2006) in nonlinear polymeric photonic crystals at the Technical University Hamburg-Harburg (Germany) and carried out his physics studies with the main focus on applied physics at the University of Hamburg (Germany).

Reference

Alessandro Tuniz1, Mario Chemnitz1,2, Jan Dellith1, Stefan Weidlich1,3, Markus A. Schmidt1,2,4. Hybrid-Mode-Assisted Long-Distance Excitation of Short-Range Surface Plasmons in a Nanotip-Enhanced Step-Index Fiber. Nano Letters volume 17 (2017) pages 631−637.

Show Affiliations
  1. Leibniz Institute of Photonic Technology (IPHT Jena), Albert-Einstein-Strasse 9, 07745 Jena, Germany
  2. Abbe School of Photonics and Faculty of Physics, Max-Wien-Platz 1, 07743 Jena, Germany
  3. Heraeus Quarzglas GmbH & Co. KG, Quarzstrasse 8, 63450 Hanau, Germany
  4. Otto Schott Institute of Materials Research, Fraunhoferstrasse 6, 07743 Jena, Germany

 

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