Ultra-narrowband dielectric metamaterial absorber with ultra-sparse nanowire grids for sensing applications

Abstract

Due to their low losses, dielectric metamaterials provide an ideal resolution to construct ultranarrowband absorbers. To improve the sensing performance, we present numerically a near-infrared ultra-narrowband absorber by putting ultra-sparse dielectric nanowire grids on metal substrate in this paper. The simulation results show that the absorber has an absorption rate larger than 0.99 with full width at half-maximum (FWHM) of 0.38 nm. The simulation field distribution also indicates that the ultra-narrowband absorption is originated from the low loss in the guided-mode resonance. thanks to the ultra-narrow absorption bandwidths and the electric field mainly distributed out of the ultra-sparse dielectric nanowire grids, our absorber has a high sensitivity S of 1052 nm/RIU and a large figure of merit (FOM) of 2768 which mean that this ultra-narrowband absorber can be applied as a high-performance refractive index sensor.Metamaterials are built with artificially constructed materials which can be manipulated to produce exotic optical properties such as super-lenses 1 , negative refraction 2 , asymmetric transmission 3 , cloaking 4 and absorbers 5 . Among them, metamaterials absorbers, which can realize near-perfect absorption by designing the nanostructures, are very appealing because they can be applied in photodetectors 6,7 , sensors 8 , thermo-photovoltaics (TPV) 9 , thermal emitters 10,11 , and solar cells 12,13 . So far, a variety of metamaterials absorbers have been proposed with different bandwidths to meet the different application demands. To achieve high performance, lots of efforts have been devoted to broadening or narrowing the absorption bandwidths [14][15][16][17][18] . For example, the broadband absorbers are usually designed to be applied in photodetectors and solar cells 19,20 . On the other hand, the absorbers with narrower absorption bandwidth have better performance in the applications of thermal emitters and sensors 8,21 . Up to date, some ultra-narrowband absorbers have been proposed by manipulating electromagnetic resonance in metallic microstructures [22][23][24][25][26] .In recent years, it has been found that dielectric metamaterials (DMs) composed of dielectric microstructures can also be used to manipulate electromagnetic resonance [27][28][29][30][31][32] . Due to the unique advantage of the low loss, dielectric metamaterials provide an ideal resolution for narrowing the absorption bandwidth [33][34][35] . In addition, the ultra-narrowband absorbers were reported by using dielectric microstructures recently 36,37 . However, how to improve the sensing performance of a dielectric metamaterial absorber is still under exploration. On the other hand, it is well known that the sensing performance of an absorber can be evaluated by sensitivity = The absorption properties of the proposed structure can be explored by the reflectance spectra. In the experiment setup, a tungsten lamp can be used as the broadband light source. The resonance absorption peaks can be achieved with a spectrometer. In ...

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