In the last decade, and driven by the strong development of nanotechnology, there has been an increased interest in the study of the optical properties of metallic nanostructures and nanoparticles and their ability to control and manipulate light. In particular, it was found that tailor designed nanostructured materials offers the possibility to control propagation, localization, and polarization of light at the nanoscale and beyond the intrinsic properties of the constituent material. A current focal point of research is, thereby, the development of novel nanostructured composite materials (metamaterials) with “designed” and tunable optical properties. These novel materials exploit the capability of metallic nanoparticles to confine the electromagnetic (EM) field beyond the diffraction limit when properly excited by the electromagnetic field of a light beam impinging on them (plasmon resonance). This property offers a way to beat the light diffraction limit and enable a path towards subwavelength optics to be used to develop nano-photonics devices. Equivalently interesting, is the strong dependence of this EM field confinement effect on the environment that offers a clear pathway to the development of ultrasensitive (at the single molecule level) sensors for environmental and biological applications.

Particularly interesting are composite metamaterials made of ferromagnetic nanoelements because they combine the plasmonic behavior described above with intertwined optical and magnetic properties (magneto-optical activity, see Fig. 1) [1-4]. Such multifunctional magneto-plasmonic metamaterials may open new views towards applications to variety of emerging technologies as, e.g., magnetoplasmonic rulers (dimers that are able to report the nanoscale distances) [5], ultrasensitive molecular sensing (see Fig. 2) [6,13], opto-activated nanomagnetic logic devices [14], and ultrathin optical metadevices (flat nano-optics) [7-9,15]. 

The goal of the present master/PhD project is the experimental exploration and control of the mutual relations between magnetism and optical properties of ferromagnetic composite metamaterials combining MO-activity and plasmonic behavior. To this purpose, laser-based measurement spectrometers that measure light intensity/polarization and intensity/polarization changes with a very high degree of precision are required. One such example is the experimental MOKE (Magneto Optical Kerr Effect) spectrometer (SpectroMOKE) at nanoGUNE that measures light intensity/polarization changes, which are caused by the magnetic properties of materials, including arrays of magnetic nano-objects, in the spectral region from 400 to 1800 nm.

The spectroMOKE set-up will be utilized to measure the optical and MO spectral response of metamaterials made of ferromagnetic-alloys and multilayered nano-structures of several sizes and shape deposited on a dielectric substrate, that will be also fabricated in our laboratory. The acquired data will then be analyzed using advanced modeling tools based on electromagnetic theory, which has been specifically devised to deal with nano-scale optical objects.

Fig. 1 Electromagnetic field confinement effect due to the excitation of a localized plasmon in a metallic nanostructure(left panel); (panels a, b, and c) example of a nanofotonic device for light polarization manipulation.

Fig. 2 Light polarization manipulation enabled by phase compensation in the optical response of a magneto-plasmonic Ni nanoantenna and its exploitation for ultrasensitive sensing.

References

[1] J. Chen et al., Small 7, 2341 (2011)

[2] V. Bonanni et al., Nano Lett. 11, 5333 (2011)

[3] N. Maccaferri et al., Phys. Rev. Lett. 111, 167401 (2013)

[4] N. Maccaferri et al., Opt. Express 21, 9875 (2013)

[5] I. Zubritskaya et al., Nano Lett. 15, 3204 (2015)

[6] N. Maccaferri et al., Nature Commun. 6, 6150 (2015)

[7] K. Lodewijks et al., Nano Lett. 14, 7207 (2014)

[8] M. Kataia et al., Nature Commun. 6, 7072 (2015)

[9] N. Maccaferri et al., Nano Lett. 16, 2533 (2016)

[10] R. Verre et al., Nanoscale 8, 10576 (2016) 

[11] M. Kataia et al., Opt. Express 24, 3652 (2016)

[12] N. Maccaferri et al., ACS Photonics 2, 1769 (2015) 

[13] A. López et al., Nanoscale 10, 18672 (2018).

[14] P. Vavassori and M. Pancaldi, Naemi Leo, and P. Vavassori, in press on Nanoscale.

[15] A. López et al., submitted to Nat. Nanotech.

Short description of the group:

The Nanomagnetism Group at CIC nanoGUNE is conducting world-class basic and applied research in the field of magnetism in nano-scale structures. The Group staff has a longstanding expertise and proven track record in fundamental and applied aspects of nano-magnetism, and specifically in the use of magneto-optical methods. The main scientific topics pursued by the Nanomagnetism Group are:

- understanding magnetism and magnetic phenomena on very small length and very fast time scales in systems with competing interactions by means of experiments and theory

- development of advanced methodologies and tooling for magnetic materials characterization at the nanometer-length scale and the picosecond-timescale (especially magneto-optics)

- design, fabrication and characterization of novel nanometer-scale magnetic structures, meta-magnetic materials, thin films and multilayers

- novel concepts for applied magnetic nano-scale materials

More info: http://www.nanogune.eu/en/research/nanomagnetism 

Application:

If you are a master student and you are interested in this project, please get in touch with the scientist in charge: Paolo Vavassori (p.vavassori@nanogune.eu)

To apply for a master scholarship fill in the form below and follow the instructions and recomendations of the general call open until 30 June 2020.