Magneto-Optical Intensity Effect in Plasmonic Structures with Gain

Olga Borovkova Magneto-Optics, Plasmonics, and Nanophotonics, Russian Quantum Center, Skolkovo, Russia Andrey Kalish Magneto-Optics, Plasmonics, and Nanophotonics, Russian Quantum Center, Skolkovo, Russia Faculty of Physics, M.V. Lomonosov Moscow State University, Moscow, Russia Petr Vetoshko Magneto-Optics, Plasmonics, and Nanophotonics, Russian Quantum Center, Skolkovo, Russia Vladimir Belotelov Magneto-Optics, Plasmonics, and Nanophotonics, Russian Quantum Center, Skolkovo, Russia Faculty of Physics, M.V. Lomonosov Moscow State University, Moscow, Russia

Over the last decade, surface plasmon-polaritons are intensively studied by many researchers and find applications in various fields, like spectroscopy, nanophotonics, biosensing, circuitry etc. It is worth mentioning also that surface plasmon-polaritons provide ample opportunities for light control in magnetic materials. In particular, SPPs can be applied for the enhancement of the magneto-optical intensity effects that are modulation of the transmitted or reflected light intensity taking place when magnetization of a plasmonic structure is reversed. Excitation of the SPPs at the interface between a metal and a ferromagnetic dielectric influences on the optical properties of the material and increases the interaction area of light and the ferromagnet. This phenomenon is known as enhancement of the transverse magneto-optical Kerr effect (TMOKE) in magnetoplasmonic structures [1]. The enhancement factor could be as large as 103. However, SPPs in such magnetoplasmonic structures suffer from absorption in both metal and dielectric media that limits plasmon mediated increase of the magneto-optical effects.

In this work we investigate how gain in a ferromagnetic dielectric influences the TMOKE enhancement level in the plasmonic crystals. The ferromagnetic layer is doped by Er3+ or Nd3+ ions to make this layer an active medium. Surface plasmon-polaritons in active media have been investigated in nonmagnetic materials, like dye solution, PMMA doped by quantum dots, etc. (see review [2]). The doped ferromagnet layer can compensate the losses of the SPP and even amplify it.

We considere a magnetoplasmonic crystal of one dimensional gold grating deposited on the doped bismuth substituted rare-earth iron garnet grown on top of the non-magnetic gadolinium gallium garnet substrate. The gold grating provides increased transmission in comparison with a smooth one. It allows to observe the TMOKE in transmission as well. We demonstrate that gain in the magnetoplasmonic crystal leads to further pronounced increase of the TMOKE. We address the dependences of the TMOKE, transmittance and reflectance spectra on the value of the gain parameter and on the geometrical parameters of the magnetoplasmonic crystal and type of the dopants. Experimental observation of this phenomenon is discussed.

[1]. V.I. Belotelov and et al, Nature Nanotech., Vol. 6, 370-376 (2011).

[2]. P. Berini, and I. De Leon, Nature Photon., Vol. 6, 16-24 (2012).

o.borovkova@rqc.ru









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