We propose a design of an ultra-broadband absorber based on a thin metamaterial nanostructure composed of a periodic array of titanium-silica (Ti-SiO) cubes and an aluminum (Al) bottom film. The proposed structure can achieve nearly perfect absorption with an average absorbance of 97% spanning a broad range from visible to near-infrared (i.e., from 354 nm to 1066 nm), showing a 90% absorption bandwidth over 712 nm, and the peak absorption is up to 99.8%. The excitation of superior surface plasmon resonance combined with the resonance induced by the metal-insulator-metal Fabry-Perot (FP) cavity leads to this broadband perfect absorption. The polarization and angle insensitivity is demonstrated by analyzing the absorption performance with oblique incidences for both TE- and TM-polarized waves. In addition, we discuss the impact of various metal materials and geometry structure on absorption performance in detail. The proposed broadband metamaterial absorber shows a promising prospect in applications such as solar cell, infrared detection, and imaging. Moreover, the use of a thin titanium cap and an aluminum film instead of noble metals has the potential to reduce production cost in applications.
Synthesizing quantum dots (QDs) using simple methods and utilizing them in optoelectronic devices are active areas of research. In this paper, we fabricated SnSe2 QDs via sonication and a laser ablation process. Deionized water was used as a solvent, and there were no organic chemicals introduced in the process. It was a facile and environmentally-friendly method. We demonstrated an ultraviolet (UV)-detector based on monolayer graphene and SnSe2 QDs. The photoresponsivity of the detector was up to 7.5 × 106 mAW−1, and the photoresponse time was ~0.31 s. The n–n heterostructures between monolayer graphene and SnSe2 QDs improved the light absorption and the transportation of photocarriers, which could greatly increase the photoresponsivity of the device.
We investigated a multiband metamaterial absorber composed of one-side open cavities. A metallic sidewall effectively prevents destructive coupling between the neighboring cavities. Thus, the number of subunits in one period, which determines the number of multibands or the width of broadband, can be greatly increased. A redshift effect of the resonances is observed theoretically and numerically when the distance between the subunits is reduced. Although the separation is very small and the coupling between the neighboring cavities is strong, the angular insensitivity of the absorption is well-maintained over a wide range. Our findings may enable applications of ultra-compact multiband sensors and thermal emitters.
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