| 1. |
- Bonanni, Valentina, et al.
(författare)
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Designer Magnetoplasmonics with Nickel Nanoferromagnets
- 2011
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Ingår i: Nano letters (Print). - : American Chemical Society (ACS). - 1530-6984 .- 1530-6992. ; 11:12, s. 5333-5338
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Tidskriftsartikel (refereegranskat)abstract
- We introduce a new perspective on magnetoplasmonics in nickel nanoferromagnets by exploiting the phase tunability of the optical polarizability due to localized surface plasmons and simultaneous magneto-optical activity. We demonstrate how the concerted action of nanoplasmonics and magnetization can manipulate the sign of rotation of the reflected light's polarization (i.e., to produce Kerr rotation reversal) in ferromagnetic nanomaterials and, further, how this effect can be dynamically controlled and employed to devise conceptually new schemes for biochemosensing.
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| 2. |
- Chen, Jianing, et al.
(författare)
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Plasmonic Nickel Nanoantennas
- 2011
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Ingår i: SMALL. - : Wiley. - 1613-6810 .- 1613-6829. ; 7:16, s. 2341-2347
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Tidskriftsartikel (refereegranskat)abstract
- The fundamental optical properties of pure nickel nanostructures are studied by far-field extinction spectroscopy and optical near-field microscopy, providing direct experimental evidence of the existence of particle plasmon resonances predicted by theory. Experimental and calculated near-field maps allow for unambiguous identification of dipolar plasmon modes. By comparing calculated near-field and far-field spectra, dramatic shifts are found between the near-field and far-field plasmon resonances, which are much stronger than in gold nanoantennas. Based on a simple damped harmonic oscillator model to describe plasmonic resonances, it is possible to explain these shifts as due to plasmon damping.
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| 3. |
- Maccaferri, Nicolò, et al.
(författare)
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Effects of a non-absorbing substrate on the magneto-optical Kerr response of plasmonic ferromagnetic nanodisks
- 2014
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Ingår i: Physica Status Solidi (a) applications and materials science. - : Wiley. - 1862-6300 .- 1862-6319. ; 211:5, s. 1067-1075
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Tidskriftsartikel (refereegranskat)abstract
- Magnetoplasmonics is an emerging field of intense research on materials combining magnetic and plasmonic functionalities. The novel optical and magneto-optical (MO) properties displayed by these materials could allow the design of a new class of magnetically controllable optical nano-devices. In this work, we investigate the effects of a non-absorbing (insulating) substrate on the MO activity of pure ferromagnetic disk-shaped nanostructures supporting localized plasmon resonances. We show that the red-shift of the localized plasmon resonance, related to the modification of the localization of the electromagnetic field due to the substrate, is not the only effect that the substrate has on the MO response. We demonstrate that the reflectivity of the substrate itself plays a key role in determining the MO response of the system. We discuss why it is so and provide a description of the modeling tools suitable to take into account both effects. Understanding the role of the substrate will permit a more aware design of magnetoplasmonic nanostructured devices for future biotechnological and optoelectronic applications. [GRAPHICS] Ferromagnetic nickel nanodisk in vacuum (left) and on a non-absorbing substrate (right), illuminated by linearly polarized light. The polarization of the reflected field is changed in the first case due to a combination of intrinsic magneto-optical properties and the nanoconfinement of the material. In the second case, the polarization of the reflected light is affected also by the presence of the substrate.
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| 4. |
- Maccaferri, N., et al.
(författare)
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Polarizability and magnetoplasmonic properties of magnetic general nanoellipsoids
- 2013
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Ingår i: Optics Express. - 1094-4087 .- 1094-4087. ; 21:8, s. 9875-9889
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Tidskriftsartikel (refereegranskat)abstract
- An approach to compute the polarizability tensor of magnetic nanoparticles having general ellipsoidal shape is presented. We find a surprisingly excellent quantitative agreement between calculated and experimental magneto-optical spectra measured in the polar Kerr configuration from nickel nanodisks of large size (exceeding 100 nm) with circular and elliptical shape. In spite of its approximations and simplicity, the formalism presented here captures the essential physics of the interplay between magneto-optical activity and the plasmonic resonance of the individual particle. The results highlight the key role of the dynamic depolarization effects to account for the magneto-optical properties of plasmonic nanostructures.
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| 5. |
- Maccaferri, N., et al.
(författare)
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Tuning the Magneto-Optical Response of Nanosize Ferromagnetic Ni Disks Using the Phase of Localized Plasmons
- 2013
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Ingår i: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 111:16
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Tidskriftsartikel (refereegranskat)abstract
- We explore the influence of the phase of localized plasmon resonances on the magneto-optical activity of nanoferromagnets. We demonstrate that these systems can be described as two orthogonal damped oscillators coupled by the spin-orbit interaction. We prove that only the spin-orbit induced transverse plasmon plays an active role on the magneto-optical properties by controlling the relative amplitude and phase lag between the two oscillators. Our theoretical predictions are fully confirmed by magneto-optical Kerr effect and optical extinction measurements in nanostructures of different size and shape.
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| 6. |
- Maccaferri, Nicolò, et al.
(författare)
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Ultrasensitive and label-free molecular-level detection enabled by light phase control in magnetoplasmonic nanoantennas
- 2015
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Ingår i: Nature Communications. - : Springer Science and Business Media LLC. - 2041-1723. ; 6
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Tidskriftsartikel (refereegranskat)abstract
- Systems allowing label-free molecular detection are expected to have enormous impact on biochemical sciences. Research focuses on materials and technologies based on exploiting localized surface plasmon resonances in metallic nanostructures. The reason for this focused attention is their suitability for single-molecule sensing, arising from intrinsically nanoscopic sensing volume and the high sensitivity to the local environment. Here we propose an alternative route, which enables radically improved sensitivity compared with recently reported plasmon-based sensors. Such high sensitivity is achieved by exploiting the control of the phase of light in magnetoplasmonic nanoantennas. We demonstrate a manifold improvement of refractometric sensing figure-of-merit. Most remarkably, we show a raw surface sensitivity (that is, without applying fitting procedures) of two orders of magnitude higher than the current values reported for nanoplasmonic sensors. Such sensitivity corresponds to a mass of similar to 0.8 ag per nanoantenna of polyamide-6.6 (n = 1.51), which is representative for a large variety of polymers, peptides and proteins.
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| 7. |
- Pirzadeh Irannezhad, Zhaleh, 1985
(författare)
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ON THE COUPLING OF THE LOCALIZED PLASMON AND INTERBAND TRANSITIONS IN NICKEL NANOANTENNAS
- 2013
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Interaction of light with metallic nanostructures smaller than the wavelength leads to excitation of collective oscillations of “free” conduction electrons. This effect leads to locally enhanced electric fields inside and outside the nanoparticle and is called localized surface plasmon resonance (LSPR). The history of this phenomenon goes back to 4th century where metallic nanoparticles were used to stain glass windows in medieval church windows. It was not until hundred years ago, however, that the physics behind the vibrant colors of noble metal nanoparticles was studied and understood - a development that ultimately resulted in the foundation of a new field in nanoscience, nanoplasmonics. Nickel (Ni) is a transition metal, which is mainly used in the preparation of alloys due to its strength, ductility and resistance to corrosion and heat. In nanoplasmonics, this metal has so far received much less attention than the “classic” plasmonic metals such as gold or silver. This is mainly due to its high ohmic losses and electronic interband transitions, which induces large damping to its LSPR. However, since most metals feature local or broad interband transitions, it is crucial to gain deeper fundamental understanding of their interaction with the plasmonic excitations. As Ni features a spectrally localized interband transition at 4.7 eV is a very good “model system” to scrutinize the LSPR-interband transition interaction. The latter is crucial in view of an increasing number of metals being considered for nanoplasmonic applications. In this thesis, the interaction between a spectrally localized interband transition and LSPR in nickel nanodisks is studied as a model system. This was done by spectrally tuning the LSPR by engineering of the nickel nanoantenna geometry or by tuning the refractive index of the surrounding medium. Using this approach, we show both experimentally and theoretically that the plasmon-interband interaction can be understood in the classical picture of two coupled harmonic oscillators, which approach a strong coupling regime. That is characterized by characteristic “energy anticrossing” behavior. These results can be generalized to all plasmonic metals, which feature spectrally localized interband transitions, and contribute to the general fundamental understanding of the role of interband transitions in plasmonic systems.
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| 8. |
- Pirzadeh Irannezhad, Zhaleh, 1985, et al.
(författare)
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Plasmon-Interband Coupling in Nickel Nanoantennas
- 2014
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Ingår i: ACS Photonics. - : American Chemical Society (ACS). - 2330-4022. ; 1:3, s. 158-162
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Tidskriftsartikel (refereegranskat)abstract
- Plasmonic excitations are usually attributed to the free electron response at visible frequencies in the classic plasmonic metals Au and Ag. However, the vast majority of metals exhibit spectrally localized interband transitions or broad interband transition backgrounds in the energy range of interest for nanoplasmonics. Nevertheless, the interaction of interband transitions with localized plasmons in optical nanoantennas has hitherto received relatively little attention, probably because interband transitions are regarded as highly unwanted due to their strong damping effect on the localized plasmons. However, with an increasing number of metals (beyond Au and Ag) being considered for nanoplasmonic applications such as hydrogen sensing (Pd), UV-SERS (Al), or magnetoplasmonics (Ni, Fe, Co), a deeper conceptual understanding of the interactions between a localized plasmon mode and an interband transition is very important. Here, as a generic example, we examine the interaction of a localized (in energy space) interband transition with spectrally tunable localized plasmonic excitations and unearth the underlying physics in a phenomenological approach for the case of Ni disk nanoantennas. We find that plasmon interband interactions can be understood in the classical picture of two coupled harmonic oscillators, exhibiting the typical energy anticrossing fingerprint of a coupled system approaching the strong-coupling regime.
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