Abstract
We study how to enhance the transverse magneto-optical Kerr effect (TMOKE) of ultra-thin magnetic dielectric films through the excitation of strong magnetic resonances on metasurface with a metal nanowire array stacked above a metal substrate with an ultra-thin magnetic dielectric film spacer. The plasmonic hybridizations between the Au nanowires and substrate result in magnetic resonances. The periodic arrangement of the Au nanowires can excite propagating surface plasmon polaritons (SPPs) on the metal surface. When the SPPs and the magnetic resonances hybridize, they can strongly couple to form two strong magnetic resonances, which are explained by a coupled oscillator model. Importantly, benefitting from the strong magnetic resonances, we can achieve a large TMOKE signal up to 26% in the ultra-thin magnetic dielectric film with a thickness of only 30 nm, which may find potential applications in nanophotonics, magnonics, and spintronics.
Highlights
Obtaining the enhancement of magnetic fields in the visible frequency has become as important in nanophotonics as obtaining the enhancement of electric fields, stemming from many applications, for example, magnetic sensors or magnetic nonlinearity [1,2,3,4,5,6,7,8,9]
By coupling with some narrow-band optical resonances such as the lattice surface modes [11,12], waveguide modes [13,14], or Bloch surface waves [15], the strong magnetic resonances have been obtained on metasurfaces, which exhibit a huge enhancement of magnetic fields
We have theoretically shown that if such a coupling appears between the surface plasmon polaritons (SPPs) and the magnetic resonances in periodic arrays of metallic nanowires on an ultra-thin dielectric film spacer deposited on a very thick metal film, a 2143-fold magnetic field enhancement can be achieved in the ultra-thin dielectric film [16]
Summary
Accepted: 21 October 2021Recently, obtaining the enhancement of magnetic fields in the visible frequency has become as important in nanophotonics as obtaining the enhancement of electric fields, stemming from many applications, for example, magnetic sensors or magnetic nonlinearity [1,2,3,4,5,6,7,8,9]. It is very important to seek new mechanisms to enhance the magnetic field component of light. Like the electric plasmonic resonances, the interactions between the magnetic resonances and other optical resonances in metasurfaces have been proposed to enhance the magnetic fields, which are still studied rarely. By coupling with some narrow-band optical resonances such as the lattice surface modes [11,12], waveguide modes [13,14], or Bloch surface waves [15], the strong magnetic resonances have been obtained on metasurfaces, which exhibit a huge enhancement of magnetic fields. We have theoretically shown that if such a coupling appears between the SPPs and the magnetic resonances in periodic arrays of metallic nanowires on an ultra-thin dielectric film spacer deposited on a very thick metal film, a 2143-fold magnetic field enhancement can be achieved in the ultra-thin dielectric film [16]
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