Browsing by Author "Niu, Chao"

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    Excitonic Resonant Emission–Absorption of Surface Plasmons in Transition Metal Dichalcogenides for Chip-Level Electronic–Photonic Integrated Circuits
    (American Chemical Society, 2016) Zhu, Zhuan; Yuan, Jiangtan; Zhou, Haiqing; Hu, Jonathan; Zhang, Jing; Wei, Chengli; Yu, Fang; Chen, Shuo; Lan, Yucheng; Yang, Yao; Wang, Yanan; Niu, Chao; Ren, Zhifeng; Lou, Jun; Wang, Zhiming; Bao, Jiming
    The monolithic integration of electronics and photonics has attracted enormous attention due to its potential applications. A major challenge to this integration is the identification of suitable materials that can emit and absorb light at the same wavelength. In this paper we utilize unique excitonic transitions in WS2 monolayers and show that WS2 exhibits a perfect overlap between its absorption and photoluminescence spectra. By coupling WS2 to Ag nanowires, we then show that WS2 monolayers are able to excite and absorb surface plasmons of Ag nanowires at the same wavelength of exciton photoluminescence. This resonant absorption by WS2 is distinguished from that of the ohmic propagation loss of silver nanowires, resulting in a short propagation length of surface plasmons. Our demonstration of resonant optical generation and detection of surface plasmons enables nanoscale optical communication and paves the way for on-chip electronic–photonic integrated circuits.
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    Quantum plasmonic control of trions in a picocavity with monolayer WS2
    (AAAS, 2019) He, Zhe; Han, Zehua; Yuan, Jiangtan; Sinyukov, Alexander M.; Eleuch, Hichem; Niu, Chao; Zhang, Zhenrong; Lou, Jun; Hu, Jonathan; Voronine, Dmitri V.; Scully, Marlan O.
    Monitoring and controlling the neutral and charged excitons (trions) in two-dimensional (2D) materials are essential for the development of high-performance devices. However, nanoscale control is challenging because of diffraction-limited spatial resolution of conventional far-field techniques. Here, we extend the classical tip-enhanced photoluminescence based on tip-substrate nanocavity to quantum regime and demonstrate controlled nano-optical imaging, namely, tip-enhanced quantum plasmonics. In addition to improving the spatial resolution, we use the scanning probe to control the optoelectronic response of monolayer WS2 by varying the neutral/charged exciton ratio via charge tunneling in Au-Ag picocavity. We observe trion “hot spots” generated by varying the picometer-scale probe-sample distance and show the effects of weak and strong coupling, which depend on the spatial location. Our experimental results are in agreement with simulations and open an unprecedented view of a new range of quantum plasmonic phenomena with 2D materials that will help to design new quantum optoelectronic devices.