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We present a simple metasurface consisting of a periodic array of two closely spaced Ag nanowires standing on Ag substrate, to achieve a very strong magnetic plasmon (MP) resonance. We show that the strong MP resonance in the simple metasurface is essentially an antisymmetric resonance caused by the near-field plasmon hybridization in the pair of metallic nanowires. The magnetic field intensity and the spectral linewidth of the MP resonance can be effectively tuned by changing the height of nanowires and the spacing between the two closely spaced nanowires. More importantly, owing to the huge magnetic field enhancement, the ultra-narrow linewidth and the nearly-zero reflection at the strong MP resonance, the metasurface has very high sensitivity (S = 750 nm/RIU, S* = 45/RIU) and figure of merit (FOM = 94, FOM* = 750000). The results suggest that the proposed simple metasurface may find great potential applications in label-free biosensing. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Achieving perfect electromagnetic wave absorption with a sub-nanometer bandwidth is challenging, which, however, is desired for high-performance refractive-index sensing. In this work, we theoretically study metasurfaces for sensing applications based on an ultra-narrow band perfect absorption in the infrared region, whose full width at half maximum (FWHM) is only 1.74 nm. The studied metasurfaces are composed of a periodic array of cross-shaped holes in a silver substrate. The ultra-narrow band perfect absorption is related to a hybrid mode, whose physical mechanism is revealed by using a coupling model of two oscillators. The hybrid mode results from the strong coupling between the magnetic resonances in individual cross-shaped holes and the surface plasmon polaritons on the top surface of the silver substrate. Two conventional parameters, sensitivity (S) and figure of merit (FOM), are used to estimate the sensing performance, which are 1317 nm/RIU and 756, respectively. Such high-performance parameters suggest great potential for the application of label-free biosensing. [ABSTRACT FROM AUTHOR]

Electrically modulating and switching the light absorption properties of monolayer graphene in near-infrared region has potentials in optoelectronic devices (e.g., photodetectors) and optical communication systems (e.g., modulators). In this work, we demonstrate numerically a broadband near-infrared absorption enhancement of monolayer graphene, due to the magnetic dipole resonance in metamaterials. The broadband light absorption in monolayer graphene can be largely modulated to realize an electrically switchable effect, via bias voltage for the interband transition of graphene to be near the magnetic dipole resonance. The absorption modulation depth is able to vary quickly from almost zero to nearly 100% in a very narrow wavelength range around the interband transition. Electrically modulating and switching the light absorption properties of monolayer graphene in near-infrared region has potentials in optoelectronic devices (e.g., photodetectors) and optical communication systems (e.g., modulators). In this work, we firstly demonstrate numerically a broadband near-infrared absorption enhancement of monolayer graphene, due to the magnetic dipole resonance in metamaterials. Then, we show that the broadband light absorption in monolayer graphene can be largely modulated to realize an electrically switchable effect, via bias voltage for the interband transition of graphene to be near the magnetic dipole resonance. The absorption modulation depth is able to vary quickly from almost zero to nearly 100% in a very narrow wavelength range around the interband transition. Image 107 [ABSTRACT FROM AUTHOR]