Layered two-dimensional materials have shown novel optoelectronic properties and are well suited to be integrated in planar photonic circuits [1][2][3] . For example, graphene has been utilized for wideband photodetection [4][5][6][7] . Because graphene lacks a band gap, however, graphene photodetectors suffer from very high dark current 6,8 . In contrast, layered black phosphorous, the latest addition to the family of 2D materials [9][10][11] , is well-suited for photodetector applications due to its narrow but finite band gap [12][13][14][15][16][17] . Here, we demonstrate a gated multilayer black phosphorus photodetector integrated on a silicon photonic waveguide operating in the near-infrared telecom band. In a significant advantage over graphene devices, black phosphorus photodetectors can operate under a bias with very low dark current and attain intrinsic responsivity up to 135 mA/W and 657 mA/W in 11.5nm and 100 nm thick devices, respectively, at room temperature. The photocurrent is dominated by the photovoltaic effect with a high response bandwidth exceeding 3 GHz. Two-dimensional (2D) materials have tremendous potential for optoelectronic applications [1][2][3] . Graphene, the most extensively investigated 2D material, has many novel optical properties such as a tunable inter-band transition and saturable absorption, and has potential for a wide range of optoelectronic applications 1,2 . However, one important optoelectronic device application where graphene is severely limited in is photodetection. Although graphene has shown broadband optical absorption, ultrafast photoresponse and reasonable responsivity, graphene photodetectors have very high dark current when they are operated in photoconductive mode

We demonstrate the integration of a black phosphorus photodetector in a hybrid, three-dimensional architecture of silicon photonics and metallic nanoplasmonics structures. This integration approach combines the advantages of the low propagation loss of silicon waveguides, high-field confinement of a plasmonic nanogap, and the narrow bandgap of black phosphorus to achieve high responsivity for detection of telecom-band, near-infrared light. Benefiting from an ultrashort channel (∼60 nm) and near-field enhancement enabled by the nanogap structure, the photodetector shows an intrinsic responsivity as high as 10 A/W afforded by internal gain mechanisms, and a 3 dB roll-off frequency of 150 MHz. This device demonstrates a promising approach for on-chip integration of three distinctive photonic systems, which, as a generic platform, may lead to future nanophotonic applications for biosensing, nonlinear optics, and optical signal processing.

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Background: As an emerging infectious disease, COVID-19 has garnered great research interest. We aimed to explore the differences between English language and Chinese language Medical/Scientific journals publications, particularly aiming to explore the efficacy/contents of the literature published in English and Chinese in relation to the outcomes of management and characterization of COVID-19 during the early stage of COVID-19 pandemic. Methods: Publications on COVID-19 research were retrieved from both English and Chinese databases. Bibliometric analyses were performed using VOSviewer 1.6.14, and CiteSpace V software. Network maps were generated to evaluate the collaborations between different authors, countries/provinces, and institutions. Results: A total of 143 English and 721 Chinese original research articles and reviews on COVID-19 were included in our study. Most of the authors and institutions of the papers were from China before March 1st, 2020, however, the distribution of authors and institutions were mainly in developed countries or more wealthy areas of China. The range of the keywords in English publications was more extensive than those in Chinese. Traditional Chinese Medicine was seen more frequently in Chinese papers than in English. Of the 143 articles published in English, 54 articles were published by Chinese authors only and 21 articles were published jointly by Chinese and other overseas authors. Conclusions: The publications in English have enabled medical practitioners and scientists to share/exchange information, while on the other hand, the publications in the Chinese language have provided complementary educational approaches for the local medical practitioners to understand the essential and key information to manage COVID-19 in the relatively remote regions of China, for the general population with a general level of education.