Abstract
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.
Highlights
Most reported metasurfaces for perfect absorption and sensing are usually composed of a periodic array of metal nanoparticles with various shapes on the top surface of a dielectric film that is deposited on a metal substrate [1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,21,22,23,24,25,26]
In In summary, we have studied theoretically metasurfaces for high-performance refractive-resummary, we have studied theoretically metasurfaces for high-performance index sensing based on thebased ultra-narrowband perfect absorption of electromagnetic waves in fractive-index sensing on the ultra-narrowband perfect absorption of electromaginfrared region
The studied metasurfaces are composed of a periodic array of cross-shaped netic waves in infrared region
Summary
There is increasing interesting in studying the perfect absorption of electromagnetic waves for refractive-index sensing by employing metasurfaces [1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,21,22,23,24,25,26,27,28,29,30,31,32], metallic nanostructures [33,34,35,36,37,38,39,40,41,42,43,44,45,46,47,48,49,50,51,52,53,54,55,56,57,58,59,60,61], and graphene nanostructures [62,63,64,65,66,67,68,69,70,71], in violet [62], visible [1,2,3,4,5,33,34,35,36,37,38,39,40,41,42,43,63,64], infrared [6,7,8,9,10,11,12,13,14,15,16,17,44,45,46,47,48,49,50,51,52,53,54,55,56,57,65], terahertz (THz) [18,19,20,21,22,23,24,58,59,60,61,66,67,68,69,70,71], and gigahertz (GHz) [25,26]frequency regions. Magnetic resonance is able to induce a substantial magnetic dipole to interact with the magnetic field of incident electromagnetic waves, and produce an effective permeability [72]. When the impedance of artificial metasurfaces is matched with that of vacuum, the incident electromagnetic waves will be nearly completely absorbed at a certain frequency range [72]. Cong et al demonstrated experimentally the metasurface electromagnetic wave perfect absorber, which consists of a square array of cross-shaped aluminum nanoparticles on a polyimide spacer supported on a Nanomaterials 2021, 11, 63. The remarkable enhancement of electromagnetic fields at the magnetic dipolar resonance enables a very strong interaction with the analyte for ultrasensitive sensing scheme in THz frequencies
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