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- 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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- 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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- Tapani, Tilaike, et al.
(författare)
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Ultrafast charge and spin dynamics in au-ni nanostructures
- 2023
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Ingår i: 2023 conference on lasers and electro-optics europe and european quantum electronics conference, CLEO/europe-EQEC 2023. - : Institute of Electrical and Electronics Engineers (IEEE). - 9798350345995
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Konferensbidrag (refereegranskat)abstract
- We study charge and spin dynamics in hybrid Au-Ni nanostructures. Experimental results, verified by numerical modelling, reveal a modification of the ultrafast demagnetization and dynamics induced by the strong plasmonic response in the Au structure.
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