Browsing by Author "Zhang, Jun"

Now showing 1 - 4 of 4
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    Accurate measurement of nanomechanical motion in a fiber-taper nano-optomechanical system
    (AIP Publishing LLC, 2019) Zheng, Huadan; Qiu, Weiqia; Gu, Xiaohang; Zhang, Yu; Zhu, Wenguo; Huang, Bincheng; Lu, Huihui; Guan, Heyuan; Xiao, Yi; Zhong, Yongchun; Fang, Junbin; Luo, Yunhan; Zhang, Jun; Yu, Jianhui; Tittel, Frank; Chen, Zhe
    The hybrid systems that couple optical and mechanical degrees of freedom in nanoscale devices offer an unprecedented opportunity and development in laboratories worldwide. A nano-optomechanical (NOM) system that converts energy directly/inversely between optics and mechanics opens an approach to control the behavior of light and light-driven mechanics. An accurate measurement of the mechanical motion of a fiber-taper NOM system is a critical challenge. In this work, an optical microscope was used to measure the nanoscale mechanical motion of the fiber taper by introducing white light interference. The resolution of mechanical motion monitoring achieved 0.356 nm with an optomechanical efficiency of >20 nm/μW. This paper describes an approach to characterize NOM transducers between optical and mechanical signals in both classical and quantum fields.
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    Geometric compactification of moduli space of cubic surfaces and Kirwan blowup
    (2005) Zhang, Jun; Hassett, Brendan E.
    We compactify the moduli space of cubic surfaces by constructing a moduli stack of stable cubic and triploid surfaces, together with a projective coarse moduli space. We also give a detailed geometric interpretation. This compactification coincides with the Naruki Cross Ratio Variety. We also show that this compactification can be obtained by taking a certain weighted blowup along the strictly semi-stable stratum from Kirwan's stratification and partial desingularization procedures.
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    Investigating self-assembly of functionalized nanotubes and peptides by tunneling microscopy
    (2006) Zhang, Jun; Kelly, Kevin F.
    Scanning tunneling microscopy (STM) is an ideal tool for probing the chemistry and physics of these types of nanostructures. Building upon on our previous carbon nanotube research, we have investigated thiol and thiophene sidewall functionalized single-walled carbon nanotubes (SWNTs). The motivation is to use these functional groups as a means to self-assemble tubes on surfaces by exploiting the well-established Au-S chemistry. Thiol and thiophene substituted nanotubes were self-assembled on bare gold surfaces as well as inserted into hexanethiol self-assembled monolayers and imaged by STM. The thiol and thiophene functional groups work as anchors, strongly binding the SWNTs to the gold. Additionally, we have measured the size and spatial distribution of the functional groups along the nanotube sidewalls. Furthermore, we have extended this self-assembly technique to biological applications where individual fullerene-terminated peptide molecules have been successfully imaged by STM with the help of insertion into close-packed alkanethiol monolayers.
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    Studying photonic excitations of carborane and fullerene nanomachines by probe microscopy
    (2008) Zhang, Jun; Kelly, Kevin F.
    Using scanning tunneling microscopy, we have successfully imaged and characterized a variety of nanomachines based on both carborane and fullerene molecules. In addition to individual manipulation by the probe, we also investigated photon-based excitation for activating the molecular motion. In the optical regime, we studied the geometrical change of azofullerene dimers that accompanies tran-cis isomerization upon photon irradiation. Furthermore, we observed rotational excitation of fullerenes on Au(111) under microwave stimulation. The results of these studies underscore the ability to control individual molecular motions through tailored external excitations and open a new potential for nanoscale mechanical, chemical, and electrical devices.