Multifunctional Graphene Metasurface for Highly Flexible Control of Microwave Absorption.

Reconfigurable multifunctional electromagnetic absorbers have shown broad application prospects in effectively dealing with a series of problems caused by complex electromagnetic environments due to their dynamic reflection wave control characteristics. In this work, we experimentally propose a multifunctional absorber based on a graphene metasurface. Its absorption mode can be flexibly switched among three modes of dual band, broadband, and single band. The reflection amplitude in each absorption mode can be controlled simultaneously. The measurement results of the prepared graphene metasurface indicate that the absorption modes and amplitudes can be dynamically controlled by changing two independent sets of bias voltages applied to the patterned graphene sandwich structures. The proposed graphene metasurface achieves peak absorption rates above 99.9% in both dual-band and single-band absorption modes. Specifically, in the broadband absorption mode, the bandwidth with an absorption rate greater than 90% reaches 17.8 GHz. In addition, it also integrates many advantages, such as optical transparency, polarization-insensitivity, stability of oblique incidence angles, and conformability to the application targets. Therefore, the proposed graphene metasurface is expected to be applied in platforms with optical windows that require resistance to electromagnetic interference and avoidance of electromagnetic radiation.

Compact multispectral photodetectors based on nanodisk arrays atop optical cavity substrates.

It is challenging for the multi-spectral photodetector to have a compact structure, high spectral resolution, and high detection efficiency. This paper reports on a new approach for compact multi-spectral visible light detecting based on the hexagonal lattice silver nanodisk arrays atop optical cavity substrates. Through numerical calculations and optimizations of experiments, we verified that the narrow band responsivity of the photodetector was caused by coupling the surface plasmonic resonances and cavity mode. The multi-spectral photodetector exhibited that the minimum FWHM and the maximum responsivity of was achieved to be 80 nm and 91.5 mA·W-1, respectively. Besides, we also analyzed the influence of the proposed structure on the energy wastage by numerical comparison. The proposed way for multi-spectral photodetector is promising to be an excellent design for the narrow band spectral detection. The design can also be easily integrated with CMOS devices and applied to other spectral regimes for different applications.

Random color filters based on an all-dielectric metasurface for compact hyperspectral imaging.

Metasurface filters are a compact, lightweight, and inexpensive solution for the miniaturized hyperspectral imaging system. However, the emerging applicability of these filters is limited by the trade-off between spatial and spectral resolutions. In this study, we establish and experimentally demonstrate a compact hyperspectral photodetection method using random all-dielectric metasurface filters that are directly integrated on the detectors. Based on compressive sensing algorithms, the compact photodetectors can accurately reconstruct the incident spectrum in the visible range. The minimum full width at half maximum (FWHM) of the spectrum reconstructed is 4.8 nm, which fully satisfies the requirements of hyperspectral imaging. The proposed method may be applied in the design, development, and measurement of compact hyperspectral imaging systems.

Unidirectional coupling and efficient detection of near-infrared surface plasmon polaritons for on-chip optoelectronic interconnection.

Plasmonic interconnection is one kind of the possible methods to construct next-generation optoelectronic integrated circuits. In this paper, the plasmonic interconnection device based on Ge in infrared band is constructed, through efficient electron-hole pair generation, the device can achieve high photocurrent response (0.25A/W). Because of the low plasmon coupling efficiency of the conventional basic periodic gratings, this paper optimized the design of the coupling structure and improved the coupling efficiency by 4 times through constructing a binary Bragg/periodic grating coupler which can realize unidirectional plasmon coupling with a simulated extinction ratio of 12.5 dB. The devices can be easily fabricated by single-step electron beam lithography and lift-off process. The experimental results verified a 3.5 times improvement in the SPPs current of the designed plasmonic interconnection device, which provides a technical path to realize efficient plasmon transmission and detection for on-chip optoelectronic interconnection.