![]() A Howes et al further improved the Q factor to 170 by taking advantage of the unique dispersion of SiC at mid-infrared wavelengths. Using simultaneously excited electric and magnetic dipoles, strong absorption of over 70% were demonstrated in dielectric metasurfaces made of Ge and Si nanopatches, however their Q factors were still limited to less than 50. Destructive interference of the two degenerate modes leads to suppression of radiative loss and enhancement of light absorption within the lossy dielectric material. ![]() One strategy for achieving both high Q factor and strong light absorption in dielectric metamaterial is to incorporate absorptive dielectric material in a structure with two spectrally overlapped modes at the critical coupling condition. ![]() These lossless dielectric metasurfaces, however, intrinsically do not absorb light, limiting their applications in cases involving optoelectronic and photothermal conversions such as photodetection and thermal management etc. These dielectric metasurfaces enable an agile control over the phase of light, and have been applied in a number of applications such as metalens, hologram and molecular fingerprint sensing, etc. Metasurfaces made of micro and nanopillars of different materials such as Te, Si, Ge and TiO 2 have been fabricated, which exhibited sharp resonance in reflection or transmission spectrum with a Q factor up to 728. To reduce the resonance bandwidth, dielectric metamaterials have been developed by using transparent materials without metals. Though wavelength-selective light absorption is readily achievable at resonance in such MIM metamaterials, their quality (Q) factors are often less than 20 as resulted from the large Ohmic loss in metals, which presents a bandwidth limitation in consideration of spectral resolution in many applications. One common metamaterial design to realize near-perfect light absorption is the metal-insulator-metal (MIM) structure. Narrow-band light absorption of metamaterials is especially important for emerging applications such as high-resolution optical filtering, wavelength-selective photodetection, and thermophotovoltaics etc. In addition, by breaking the time-reversal symmetry with a magnetic field, novel nonreciprocal properties such as unidirectional light absorption and scattering have been reported in magnetic metamaterials, which have added new degrees of freedom for light manipulation. Based on resonance-enhanced light–matter interaction, metamaterials have become a promising platform for developing non-invasive and sensitive biosensors. With innovations in metamaterial structures and resonance modes, high efficiency light absorption has been demonstrated in a variety of spectral forms such as single-band, multi-band, or broadband spectra. Metamaterials made of periodic subwavelength units present a flexible way for manipulating light absorption properties that are not otherwise available in natural materials. These results suggest that cavity-coupling presents an effective way in reducing the resonance bandwidth and enhancing light absorption in dielectric metamaterials, which holds promise for expanding the properties and device functionalities of metamaterials. To reveal potential application of the metasurface, the Fano resonance is applied in refractive index sensing and exhibits a sensitivity of 518.75 nm RIU −1 and a figure-of-merit (FoM) of 14.82 RIU −1. The strongly absorbing Fano resonance is tunable within the 3–5 μm band by varying geometric parameters of the metasurface. The weak coupling between electric mie mode in Si cuboid and Fabry–Perot mode within the SiO 2 spacer layer yields a Fano resonance at 4.19 μm wavelength, which exhibits a strong light absorption of 65.8% and a quality (Q) factor of 112. Our fabricated metasurface consists of a Si cuboid array on top of a SiO 2 film backed with a metallic Cu layer. In this paper, we demonstrate a class of metal-dielectric thin-film cavity-coupled dielectric metasurfaces, which feature Fano resonances with both narrow bandwidth and strong light absorption. ![]() Metamaterial resonance offers a flexibility in engineering the frequency and bandwidth of light absorption for a variety of optoelectronic applications such as wavelength-selective photodetection, optical sensing and infrared camouflaging etc.
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |