Browsing by Author "Qiao, Ruixi"

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    Complete structural characterization of single carbon nanotubes by Rayleigh scattering circular dichroism
    (Nature Publishing Group, 2021-10) Yao, Fengrui; Yu, Wentao; Liu, Can; Su, Yingze; You, Yilong; Ma, He; Qiao, Ruixi; Wu, Chunchun; Ma, Chaojie; Gao, Peng; Xiao, Fajun; Zhao, Jianlin; Bai, Xuedong; Sun, Zhipei; Maruyama, Shigeo; Wang, Feng; Zhang, Jin; Liu, Kaihui; Department of Electronics and Nanoengineering; Centre of Excellence in Quantum Technology, QTF; Zhipei Sun Group; Peking University; Northwestern Polytechnical University; CAS - Institute of Physics; University of Tokyo; University of California, Berkeley
    Non-invasive, high-throughput spectroscopic techniques can identify chiral indices (n,m) of carbon nanotubes down to the single-tube level1–6. Yet, for complete characterization and to unlock full functionality, the handedness, the structural property associated with mirror symmetry breaking, also needs to be identified accurately and efficiently7–14. So far, optical methods fail in the handedness characterization of single nanotubes because of the extremely weak chiroptical signals (roughly 10−7) compared with the excitation light15,16. Here we demonstrate the complete structure identification of single nanotubes in terms of both chiral indices and handedness by Rayleigh scattering circular dichroism. Our method is based on the background-free feature of Rayleigh scattering collected at an oblique angle, which enhances the nanotube’s chiroptical signal by three to four orders of magnitude compared with conventional absorption circular dichroism. We measured a total of 30 single-walled carbon nanotubes including both semiconducting and metallic nanotubes and found that their absolute chiroptical signals show a distinct structure dependence, which can be qualitatively understood through tight-binding calculations. Our strategy enables the exploration of handedness-related functionality of single nanotubes and provides a facile platform for chiral discrimination and chiral device exploration at the level of individual nanomaterials.
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    Graphene photonic crystal fibre with strong and tunable light–matter interaction
    (Nature Publishing Group, 2019-08-12) Chen, Ke; Zhou, Xu; Cheng, Xu; Qiao, Ruixi; Cheng, Yi; Liu, Can; Xie, Yadian; Yu, Wentao; Yao, Fengrui; Sun, Zhipei; Wang, Feng; Liu, Kaihui; Liu, Zhongfan; Department of Electronics and Nanoengineering; Centre of Excellence in Quantum Technology, QTF; Zhipei Sun Group; Peking University; Beijing Graphene Institute; University of California, Berkeley
    The integration of photonic crystal fibre (PCF) with various functional materials has greatly expanded the application regimes of optical fibre1–12. The emergence of graphene (Gr) has stimulated new opportunities when combined with PCF, allowing for electrical tunability, a broadband optical response and all-fibre integration ability13–18. However, previous demonstrations have typically been limited to micrometre-sized samples, far behind the requirements of real applications at the metre-scale level. Here, we demonstrate a new hybrid material, Gr–PCF, with length up to half a metre, produced using a chemical vapour deposition method. The Gr–PCF shows a strong light–matter interaction with ~8 dB cm−1 attenuation. In addition, the Gr–PCF-based electro-optic modulator demonstrates a broadband response (1,150–1,600 nm) and large modulation depth (~20 dB cm−1 at 1,550 nm) under a low gate voltage of ~2 V. Our results could enable industrial-level graphene applications based on this Gr–PCF and suggest an attractive platform for two-dimensional material-PCF.
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    Optical fibres with embedded two-dimensional materials for ultrahigh nonlinearity
    (Nature Publishing Group, 2020-12) Zuo, Yonggang; Yu, Wentao; Liu, Can; Cheng, Xu; Qiao, Ruixi; Liang, Jing; Zhou, Xu; Wang, Jinhuan; Wu, Muhong; Zhao, Yun; Gao, Peng; Wu, Shiwei; Sun, Zhipei; Liu, Kaihui; Bai, Xuedong; Liu, Zhongfan; Department of Electronics and Nanoengineering; Centre of Excellence in Quantum Technology, QTF; Zhipei Sun Group; Chinese Academy of Sciences; Peking University; Beijing Institute of Technology; Fudan University
    Nonlinear optical fibres have been employed for a vast number of applications, including optical frequency conversion, ultrafast laser and optical communication1–4. In current manufacturing technologies, nonlinearity is realized by the injection of nonlinear materials into fibres5–7 or the fabrication of microstructured fibres8–10. Both strategies, however, suffer from either low optical nonlinearity or poor design flexibility. Here, we report the direct growth of MoS2, a highly nonlinear two-dimensional material11, onto the internal walls of a SiO2 optical fibre. This growth is realized via a two-step chemical vapour deposition method, where a solid precursor is pre-deposited to guarantee a homogeneous feedstock before achieving uniform two-dimensional material growth along the entire fibre walls. By using the as-fabricated 25-cm-long fibre, both second- and third-harmonic generation could be enhanced by ~300 times compared with monolayer MoS2/silica. Propagation losses remain at ~0.1 dB cm–1 for a wide frequency range. In addition, we demonstrate an all-fibre mode-locked laser (~6 mW output, ~500 fs pulse width and ~41 MHz repetition rate) by integrating the two-dimensional-material-embedded optical fibre as a saturable absorber. Initial tests show that our fabrication strategy is amenable to other transition metal dichalcogenides, making these embedded fibres versatile for several all-fibre nonlinear optics and optoelectronics applications.
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    Quiver-quenched optical-field-emission from carbon nanotubes
    (2017-09-25) Li, Chi; Zhou, Xu; Zhai, Feng; Li, Zhenjun; Yao, Fengrui; Qiao, Ruixi; Chen, Ke; Yu, Dapeng; Sun, Zhipei; Liu, Kaihui; Dai, Qing; National Center for Nanoscience and Technology Beijing; Peking University; Zhejiang Normal University; Department of Micro and Nanosciences; Department of Electronics and Nanoengineering
    Carbon nanotubes (CNTs) enable large electric field enhancement for an extremely broad bandwidth spanning from the optical domain down to static fields. This is due to their high aspect ratio, small tip radius, and high structural stability. CNTs therefore represent an ideal model-system for the investigation of nonlinear and strong-field phenomena. In this paper, we extend the range of optical-field-emission materials from metal nanostructures to CNTs. Quiver-quenched optical-field-emission (i.e., the transition to a sub-cycle regime) is observed for CNTs tips in a short-wavelength laser field of 820 nm that requires a mid-infrared excitation field of conventional metal tips emitters. This special property relies on the ultrasmall tips radius (∼1 nm) and the high optical-field enhancement (∼21.6) properties of CNTs. This study suggests that CNTs are excellent candidates for optically driven ultrafast electron sources with both high spatial and high temporal coherence. They also provide more freedom for the manipulation and control of electron dynamics at the attosecond timescale, which extends the bandwidth of light-wave electronic devices.