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Bound state in the continuum (BIC), generally realized by structures with in-plane symmetry, has been under the spotlight in the control of the electromagnetic field. This Letter presents a terahertz metasurface that possesses broken in-plane symmetry for exciting BIC. The switch from a BIC to a quasi-BIC can be achieved through parameter modulation. According to multipolar decomposition, the BIC is constructed by the destructive interference of far-field radiation originating from the electric dipole and magnetic quadrupole. More importantly, considering that the metal material has finite conductivity, we analyze the relationship between radiation and non-radiation losses, based on the time domain coupled mode theory, which provides substantial theoretical support for the investigation of BIC phenomena. Furthermore, the proposed metasurface exciting quasi-BIC is highly sensitive to the changes in the dielectric environment, resulting in a high sensitivity of 135 GHz/RIU and a distinction between sucrose and glucose with the same solid content. As a result, our research provides a theoretical explanation of the evolution of BIC excited by the structure with broken in-plane symmetry and promotes the development of the high-performance meta-device used for sensing. [ABSTRACT FROM AUTHOR]

Light absorption of suspended monolayer graphene in the ultraviolet range is relatively low, which impedes the potential applications for graphene-based optoelectronic devices. To enhance the light-matter interaction in a wide spectral range, we propose two plasmonic structures based on a metal-dielectric-metal configuration. After rigorous optimization of geometric parameters, broadband and enhanced ultraviolet light absorption of graphene can be achieved. The bandwidth above 30% absorption rate can reach up to 245 nm (from 240 nm to 485 nm), while the relative bandwidth can reach up to 68%. The optimal absorption peak is as high as 54%. Besides, the absorption spectrum can be tuned by adjusting the geometric parameters. Physical insight is revealed with electric and magnetic field distributions. Furthermore, the tolerance for the incident angle is demonstrated, and the dependence of the polarization angle is discussed. Our approach shows promising potential for novel graphene-based applications in the ultraviolet range. [ABSTRACT FROM AUTHOR]

Enhancing the light–matter interaction of graphene is an important issue for related photonic devices and applications. In view of its potential ultraviolet applications, we aim to achieve extremely high ultraviolet absorption in graphene without any nanostructure or microstructure patterning. By manipulating the polarization and angle of incident light, the ultraviolet power can be sufficiently coupled to the optical dissipation of graphene based on single-channel coherent perfect absorption in an optimized multilayered thin film structure. The ultraviolet absorbance ratios of single and four atomic graphene layers are enhanced up to 71.4% and 92.2%, respectively. Our research provides a simple and efficient scheme to trap ultraviolet light for developing promising photonic and optoelectronic devices based on graphene and potentially other 2D materials. [ABSTRACT FROM AUTHOR]

We have fabricated a metallic nanomesh using nanosphere lithography and metal evaporation. The metallic nanomesh has a precisely controlled nanostructure showing excellent uniformity with hexagonally arrayed periodic circular holes. A P3HT:PCBM organic solar cell, with the gold nanomesh electrode, demonstrates a high fill factor of 61% and a considerable power conversion efficiency of 3.12%. Electromagnetic simulation indicates that the optical properties of the metallic nanomesh can be optimized for organic photovoltaic devices by tuning the film thickness, hole diameter, and periodicity. These results show the promising potential of using a metallic nanomesh as the transparent electrode in organic solar cells. [ABSTRACT FROM AUTHOR]

Graphene emitters with high enhancement factor and ultra low emission field were exfoliated from carbon fibers in carbon cloth. This method made the graphene sheets to stay on the carbon fiber and were used, in situ, as emitters. Due to their high multistage enhancement factor and intrinsic good contact, electron emission from these graphene sheets required ultra low emission field. The threshold-field corresponding to emission current density of 1 mA/cm2 was about 0.7 V/μm. This high enhancement factor was attributed to the effects of the high aspect ratio of graphene sheets and the geometry of carbon cloth. [ABSTRACT FROM AUTHOR]