| 1. |
- Chioar, Ioan-Augustin, et al.
(författare)
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Modular magneto-optical diffractometer for the characterization of magnetoplasmonic crystals
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- We report on the development of a modular magneto-optical diffractometer designed to measure the optical and magneto-optical properties of nanostructured magnetoplasmonic crystals. The system uses monochromatic, coherent light beams with defined polarization states, for the energy- and angular-dependent measurement of reflected and transmitted beams. Polarization analysis instrumentation further enables the detailed characterisation of the polarization state of the light after the interaction with the magnetoplasmonic crystals. The magneto-optical activity is measured with the help of a quadrupole coil system, allowing for the application of magnetic fields in the plane of the samples. The instrument’s versatile design provides a toolbox of methods capable of capturing a far-field description of the optical and magneto-optical response of magnetoplasmonic crystals. We demonstrate its functionality and utility for the case of a Ni-antidot crystal.
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| 2. |
- Magnfält, Daniel, et al.
(författare)
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Synthesis of tunable plasmonic metal-ceramic nanocomposite thin films by temporally modulated sputtered fluxes
- 2017
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Ingår i: Journal of Applied Physics. - : AMER INST PHYSICS. - 0021-8979 .- 1089-7550. ; 121:17
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Tidskriftsartikel (refereegranskat)abstract
- The scientific and technological interest for metal-dielectric nanocomposite thin films emanates from the excitation of localized surface plasmon resonances (LSPRs) on the metal component. The overall optical response of the nanocomposite is governed by the refractive index of the dielectric matrix and the properties of the metallic nanoparticles in terms of their bulk optical properties, size, and shape, and the inter-particle distance of separation. In order to tune the film morphology and optical properties, complex synthesis processes which include multiple steps-i. e., film deposition followed by post-deposition treatment by thermal or laser annealing-are commonly employed. In the present study, we demonstrate that the absorption resonances of Ag/AlOxNy nanocomposite films can be effectively tuned from green (similar to 2.4 eV) to violet (similar to 2.8 eV) using a single-step synthesis process that is based on modulating the arrival pattern of film forming species with sub-monolayer resolution, while keeping the amount of Ag in the films constant. Our data indicate that the optical response of the films is the result of LSPRs on isolated Ag nanoparticles that are seemingly shifted by dipolar interactions between neighboring particles. The synthesis strategy presented may be of relevance for enabling integration of plasmonic nanocomposite films on thermally sensitive substrates. Published by AIP Publishing.
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| 3. |
- Melander, Emil, 1985-, et al.
(författare)
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Kerr effect enhancement in Ni antidot hexagonal nanostructures
- 2013
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Angular resolved transverse magneto-optical Kerr effect (TMOKE) measurements provide a versatile tool for optical characterization of plasmonic nanostructures and show how plasmons couple to the applied magnetic field. These measurements show TMOKE enhancements that are closely connected to the plasmonic resonances of the nanostructures. This is seen even without noble metal layers that are traditionally used as the most important enhancing parameter. Measurements with these methods on hexagonal arrays of circular holes in thin Ni films (Ni covered with Au [1] as well as pure Ni [2]) are presented and compared with reference Ni films. The hole sizes of the two samples are 250 nm for the Au covered Ni and 220 nm for the pure Ni, the periodicities are 470 nm for the Au covered and 450 nm for the pure Ni. The TMOKE asymmetry coincides well with the plasmonic resonance showing a large increase of the signal. Drops in reflectivity, enhanced magneto-optical activity and transmission are reported which are closely connected with the formation of surface plasmons. One signature feature of plasmons, the drop in reflectivity followed by the Fano resonance, is shown to yield an increased magneto-optical asymmetry and therefore an increased sensitivity in the measurement even though the signal-to-noise ratio from the light source is significantly decreased. By comparing the two cases one can see that even though the plasmonic signal (in reflectivity) is much smaller for the pure Ni (less than 10% change in reflectivity compared to that of the Au covered Ni) the magneto-plasmonic signal is only about 20% smaller (0.048% compared to 0.06% for the Au covered Ni) which shows that magneto-optical methods have a higher sensitivity to the plasmonic states and can also be used to characterize the magneto-plasmonic properties. With this type of patterned nanostructures, we have shown that it is possible to enhance the magneto-optical activity due to the coupling to the plasmonic resonance in pure magnetic Ni (self-passivation thickness ~1nm). This enables purely magnetic plasmonic structures (no noble metal required) and paves the way for circuits where the applied magnetization can be a great tool for controlling, enhancing and sensing the plasmonic effects.[1] E. Th. Papaioannou et al., Opt. Express 19, 23867 (2011)[2] E. Melander et al., Appl. Phys. Lett. 101, 063107 (2012)
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| 4. |
- Melander, Emil, 1985-
(författare)
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Magnetoplasmonic nanostructures
- 2016
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Surfaces that are nanopatterned, metallic, and magnetic can support surface plasmon resonances, providing an alternative and effective way to reconfigure flat optical components. Utilising a range of near- and far-field characterisation techniques, the optical and magneto-optical properties of lithographically patterned thin magnetic films are investigated.A magneto-optical diffractometer was designed, assembled, and commissioned to characterise periodic magneto-plasmonic nanostructures. For Ni and Co nanostructured antidot arrays, enhanced values of the magneto-optical Kerr rotation were recorded for energies and angles corresponding to excitations of surface plasmon polaritons. This enhancement was found to be thickness dependent. Modification of the optical properties via applied transverse magnetic fields and the excitation of surface plasmon polaritons, was demonstrated for an antidot array of pure Ni. The excitation was also shown to enhance the generation of second harmonics, as well as further activate nonlinear-optical mechanisms.In order to fully resolve and explain the source of this remarkable magneto-optical activity, near field probing techniques were used. This allows for mapping the electric near-field with a sub-wavelength resolution, thereby revealing the interplay between the light and the nanostructured lattice. The measurements show that the electric near field intensification, induced by plasmon excitation, increases the polarisation conversion, which correlates to the observed magneto-optical Kerr rotation.
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| 5. |
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| 6. |
- Melander, Emil, 1985-, et al.
(författare)
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Spectral magneto-optical tunability using Bragg plasmons
- 2015
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Magnetoplasmonics is a field where external magnetic fields are utilized to control the optical properties that come from plasmons. Active control of plasmonics has many applications in energy harvesting and nanosensing. [1]We demonstrate experimentally the optical and magnetooptical response from Bragg plasmons [2] using diffraction from magnetoplasmonic nanodisks arranged in a periodic 2D square pattern from the coupled islands. The circular islands are 450 nm in diameter and have a lateral periodicity of 512 nm. This enables diffraction parallel to the surface which in turn yields Bragg plasmon excitation due to the electric field enhancement. The alloy is a combination of Fe and Pd, Fe20Pd80, in order to have a simple material that has both the magnetic functionality as well as the plasmonic.Specular reflectivity and transverse magnetooptical Kerr effect (TMOKE) spectra [3] are compared to show how the optical measurements relate to the magnetooptical enhancement. The experimental data is compared to a simple diffraction model that accounts for the lateral dimensions of the nanostructure and the diffraction which gives the Bragg plasmon onset. In this way we show the link between the Bragg plasmon excitation and the changes in TMOKE asymmetry.[1] Gaspar Armelles and Alexandre Dmitriev, “Focus on magnetoplasmonics”, New J. Phys. 16 045012, 2014[2] Melander et al., “Spectral magnetooptical tunability from Bragg plasmons”, to be submitted[3] Melander et al., “Influence of the magnetic field on the plasmonic properties of transparent Ni anti-dot arrays”, Appl. Phys. Lett. 101, 063107 (2012)
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| 7. |
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| 8. |
- Rollinger, Markus, et al.
(författare)
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Light Localization and Magneto-Optic Enhancement in Ni Antidot Arrays
- 2016
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Ingår i: Nano letters (Print). - : American Chemical Society (ACS). - 1530-6984 .- 1530-6992. ; 16:4, s. 2432-2438
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- We reveal an explicit strategy to design the magneto-optic response of a magneto-plasmonic crystal by correlating near- and far-fields effects. We use photoemission electron microscopy to map the spatial distribution of the electric near-field on a nanopatterned magnetic surface that supports plasmon polaritons. By using different photon energies and polarization states of the incident light we reveal that the electric near-field is either concentrated in spots forming a hexagonal lattice with the same symmetry as the Ni nanopattern or in stripes oriented along the Gamma-K direction of the lattice and perpendicular to the polarization direction. We show that the polarization-dependent near-field enhancement on the patterned surface is directly correlated to both the excitation of surface plasmon polaritons on the patterned surface as well as the enhancement of the polar magneto-optical Kerr effect. We obtain a relationship between the size of the enhanced magneto optical behavior and the polarization and wavelength of optical excitation. The engineering of the magneto-optic response based on the plasmon-induced modification of the optical properties introduces the concept of a magneto-plasmonic meta-structure.
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| 9. |
- Rowan-Robinson, Richard M., et al.
(författare)
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Thickness dependent enhancement of the polar Kerr rotation in Co magnetoplasmonic nanostructures
- 2019
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Ingår i: AIP Advances. - : American Institute of Physics (AIP). - 2158-3226. ; 9:2
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Tidskriftsartikel (refereegranskat)abstract
- Large surface plasmon polariton assisted enhancement of the magneto-optical activity has been observed in the past, through spectral measurements of the polar Kerr rotation in Co hexagonal antidot arrays. Here, we report a strong thickness dependence, which is unexpected given that the Kerr effect is considered a surface sensitive phenomena. The maximum Kerr rotation was found to be -0.66 degrees for a 100 nm thick sample. This thickness is far above the typical optical penetration depth of a continuous Co film, demonstrating that in the presence of plasmons the critical lengthscales are dramatically altered, and in this case extended. We therefore establish that the plasmon enhanced Kerr effect does not only depend on the in-plane structuring of the sample, but also on the out-of-plane geometrical parameters, which is an important consideration in magnetoplasmonic device design. (c) 2019 Author(s).
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