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Kang, Evan S. H.
Publications (4 of 4) Show all publications
Chen, S., Kang, E. S. H., Shiran Chaharsoughi, M., Stanishev, V., Kuhne, P., Sun, H., . . . Jonsson, M. (2020). Conductive polymer nanoantennas for dynamicorganic plasmonics [Letter to the editor]. Nature Nanotechnology, 15, Article ID s41565-019-0583-y.
Open this publication in new window or tab >>Conductive polymer nanoantennas for dynamicorganic plasmonics
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2020 (English)In: Nature Nanotechnology, ISSN 1748-3387, E-ISSN 1748-3395, Vol. 15, article id s41565-019-0583-yArticle in journal, Letter (Refereed) Published
Abstract [en]

Being able to dynamically shape light at the nanoscale is oneof the ultimate goals in nano-optics1. Resonant light–matterinteraction can be achieved using conventional plasmonicsbased on metal nanostructures, but their tunability is highlylimited due to a fixed permittivity2. Materials with switchablestates and methods for dynamic control of light–matterinteraction at the nanoscale are therefore desired. Here weshow that nanodisks of a conductive polymer can supportlocalized surface plasmon resonances in the near-infraredand function as dynamic nano-optical antennas, with their resonancebehaviour tunable by chemical redox reactions. Theseplasmons originate from the mobile polaronic charge carriersof a poly(3,4-ethylenedioxythiophene:sulfate) (PEDOT:Sulf)polymer network. We demonstrate complete and reversibleswitching of the optical response of the nanoantennasby chemical tuning of their redox state, which modulatesthe material permittivity between plasmonic and dielectricregimes via non-volatile changes in the mobile chargecarrier density. Further research may study different conductivepolymers and nanostructures and explore their usein various applications, such as dynamic meta-optics andreflective displays.

Place, publisher, year, edition, pages
London: Nature Publishing Group, 2020
National Category
Atom and Molecular Physics and Optics
Identifiers
urn:nbn:se:liu:diva-163089 (URN)10.1038/s41565-019-0583-y (DOI)2-s2.0-85076515412 (Scopus ID)
Available from: 2020-01-10 Created: 2020-01-10 Last updated: 2020-01-14Bibliographically approved
Kang, E. S. H., Shiran Chaharsoughi, M., Rossi, S. & Jonsson, M. (2019). Hybrid plasmonic metasurfaces. Journal of Applied Physics, 126(14), Article ID 140901.
Open this publication in new window or tab >>Hybrid plasmonic metasurfaces
2019 (English)In: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 126, no 14, article id 140901Article in journal (Refereed) Published
Abstract [en]

Plasmonic metasurfaces based on ensembles of distributed metallic nanostructures can absorb, scatter, and in other ways shape light at the nanoscale. Forming hybrid plasmonic metasurfaces by combination with other materials opens up for new research directions and novel applications. This perspective highlights some of the recent advancements in this vibrant research field. Particular emphasis is put on hybrid plasmonic metasurfaces comprising organic materials and on concepts related to switchable surfaces, light-to-heat conversion, and hybridized light-matter states based on strong coupling.

Place, publisher, year, edition, pages
American Institute of Physics, 2019
National Category
Other Physics Topics
Identifiers
urn:nbn:se:liu:diva-160892 (URN)10.1063/1.5116885 (DOI)000503995300001 ()
Note

Funding agencies:  Wenner-Gren Foundations; Swedish Research CouncilSwedish Research Council; Swedish Foundation for Strategic ResearchSwedish Foundation for Strategic Research; Swedish Government Strategic Research Area in Materials Science on Functional Materials at Linko

Available from: 2019-10-14 Created: 2019-10-14 Last updated: 2020-01-09
Malekian, B., Xiong, K., Kang, E. S. H., Andersson, J., Emilsson, G., Rommel, M., . . . Dahlin, A. (2019). Optical Properties of Plasmonic Nanopore Arrays Prepared by Electron Beam and Colloidal Lithography. Nanoscale Advances
Open this publication in new window or tab >>Optical Properties of Plasmonic Nanopore Arrays Prepared by Electron Beam and Colloidal Lithography
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2019 (English)In: Nanoscale Advances, E-ISSN 2516-0230Article in journal (Refereed) Epub ahead of print
Abstract [en]

Solid state nanopores are central structures for many applications. To date, much effort has been spent on controlled fabrication of single nanopores, while relatively little work has focused on large scale fabrication of arrays of nanopores. In this work we show wafer-scale fabrication of plasmonic nanopores in 50 nm thick silicon nitride membranes with one or two 30 nm gold films, using electron beam lithography with a negative resist or a new version of colloidal lithography. Both approaches offer good control of pore diameter (even below 100 nm) and with high yield (>90%) of intact membranes. Colloidal lithography has the advantage of parallel patterning without expensive equipment. Despite its serial nature, electron beam lithography provides high throughput and can make arbitrary array patterns. Importantly, both methods prevent metal from ending up on the membrane pore sidewalls. The new fabrication methods make it possible to compare the optical properties of structurally identical plasmonic nanopore arrays with either long-range order (e-beam) or short-range order (colloidal). The resonance features in the extinction spectrum are very similar for both structures when the pitch is the same as the characteristic spacing in the self-assembled colloidal pattern. Long-range ordering slightly enhances the magnitude of the extinction maximum and blueshift the transmission maximum by tens of nm. Upon reducing the diameter in long-range ordered arrays, the resonance is reduced in magnitude and the transmission maximum is further blue shifted, just like for short-range ordered arrays. These effects are well explained by interpreting the spectra as Fano interference between the grating-type excitation of propagating surface plasmons and the broad transmission via individual pores in the metal film. Furthermore, we find that only the short-range ordered arrays scatter light, which we attribute to the highly limited effective period in the short-range ordered system and the corresponding lack of coherent suppression of scattering via interference effects.

Place, publisher, year, edition, pages
Royal Society of Chemistry, 2019
National Category
Condensed Matter Physics
Identifiers
urn:nbn:se:liu:diva-160890 (URN)10.1039/C9NA00585D (DOI)
Available from: 2019-10-14 Created: 2019-10-14 Last updated: 2019-12-04
Kang, E. S. H., Chen, S., Sardar, S., Tordera, D., Armakavicius, N., Darakchieva, V., . . . Jonsson, M. (2018). Strong Plasmon–Exciton Coupling with Directional Absorption Features in Optically Thin Hybrid Nanohole Metasurfaces. ACS Photonics, 4046-4055
Open this publication in new window or tab >>Strong Plasmon–Exciton Coupling with Directional Absorption Features in Optically Thin Hybrid Nanohole Metasurfaces
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2018 (English)In: ACS Photonics, E-ISSN 2330-4022, p. 4046-4055Article in journal (Refereed) Published
Abstract [en]

Plasmons and excitons can interact to form new hybridized light–matter states, with a multitude of potential applications including optical logic circuits and single-photon switches. Here, we report the first observation of strong coupling based on optically thin plasmonic nanohole films. The absorptive plasmon resonances of these nanohole films lead to suppressed transmission and Fano-shaped extinction peaks. We prepared silver nanohole films by colloidal lithography, which enables large-scale fabrication of nanoholes distributed in a short-range order. When coated with J-aggregate molecules, both extinction and absorption spectra show clear formation of two separated polariton resonances, with vacuum Rabi splitting on the order of 300 meV determined from anticrossing experiments. In accordance with strong coupling theory, the splitting magnitude increases linearly with the square root of molecular concentration. The extinction peak positions are blue-shifted from the absorption polariton positions, as explained by additional Fano interference between the hybridized states and the metal film. This highlights that absorption measurements are important not only to prove strong coupling but also to correctly determine hybridized polariton positions and splitting magnitudes in hybrid plasmonic nanohole systems. The polariton absorption peaks also show strong dependence on illumination direction, as found related to inherent directionality of the plasmonic nanohole metasurface and differences in light interaction with nonhybridized molecules. Importantly, optical simulations could successfully reproduce the experimental results and all coupling features. Furthermore, simulated spatial distribution of the absorption provides additional evidence of strong coupling in the hybrid nanohole system. The work paves the way toward strong coupling applications based on optically thin nanohole systems, as further promoted by the scalable fabrication.

Place, publisher, year, edition, pages
American Chemical Society (ACS), 2018
Keywords
directional absorption; Fano interferences; J-aggregates; metasurfaces; nanoholes; plasmonics; polaritons; strong coupling
National Category
Atom and Molecular Physics and Optics
Identifiers
urn:nbn:se:liu:diva-151716 (URN)10.1021/acsphotonics.8b00679 (DOI)000447954200023 ()
Note

Funding agencies: Wenner-Gren Foundations; Swedish Research Council; Swedish Foundation for Strategic Research; AForsk Foundation; Royal Swedish Academy of Sciences; Swedish Government Strategic Research Area in Materials Science on Functional Materials at Linkoping Univer

Available from: 2018-10-03 Created: 2018-10-03 Last updated: 2018-11-09
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