Design and fabrication of plasmonic cavities for magneto-optical sensing

Loughran, T.H.J. et al. (2018) Design and fabrication of plasmonic cavities for magneto-optical sensing. AIP Advances, 8(5), 055207. (doi: 10.1063/1.5021538)

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The design and fabrication of a novel plasmonic cavity, intended to allow far-field recovery of signals arising from near field magneto-optical interactions, is presented. Finite element modeling is used to describe the interaction between a gold film, containing cross-shaped cavities, with a nearby magnetic under-layer. The modeling revealed strong electric field confinement near the center of the cross structure for certain optical wavelengths, which may be tuned by varying the length of the cross through a range that is compatible with available fabrication techniques. Furthermore, the magneto optical Kerr effect (MOKE) response of the composite structure can be enhanced with respect to that of the bare magnetic film. To confirm these findings, cavities were milled within gold films deposited upon a soluble film, allowing relocation to a ferromagnetic film using a float transfer technique. Cross cavity arrays were fabricated and characterized by optical transmission spectroscopy prior to floating, revealing resonances at optical wavelengths in good agreement with the finite element modeling. Following transfer to the magnetic film, circular test apertures within the gold film yielded clear magneto-optical signals even for diameters within the sub-wavelength regime. However, no magneto-optical signal was observed for the cross cavity arrays, since the FIB milling process was found to produce nanotube structures within the soluble under-layer that adhered to the gold. Further optimization of the fabrication process should allow recovery of magneto-optical signal from cross cavity structures.

Item Type:Articles
Additional Information:Financial support from the UK Engineering and Physical Science Research Council (EPSRC) grants EP/1038470/I and EP/1038411/1 is gratefully acknowledged. We also acknowledge the support of Seagate Technology (Ireland) under SOW 00077300.0. RMB contribution to project was supported by the Royal Academy of Engineering under the Research Chairs and Senior Research Fellowships Scheme.
Glasgow Author(s) Enlighten ID:Einsle, Dr Joshua Franz
Authors: Loughran, T.H.J., Roth, J., Keatley, P.S., Hendry, E., Barnes, W.L., Hicken, R.J., Einsle, J.F., Amy, A., Hendren, W., Bowman, R.M., and Dawson, P.
College/School:College of Science and Engineering > School of Geographical and Earth Sciences > Earth Sciences
Journal Name:AIP Advances
Publisher:American Institute of Physics
ISSN (Online):2158-3226
Published Online:08 May 2018
Copyright Holders:Copyright © 2018 The Authors
First Published:First published in AIP Advances 8(5):055207
Publisher Policy:Reproduced under a Creative Commons License

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