title: Extremely strong bipolar optical interactions in paired graphene nanoribbons.
abstract: Graphene is an excellent multi-functional platform for electrons, photons, and phonons due to exceptional electronic, photonic, and thermal properties. When combining its extraordinary mechanical characteristics with optical properties, graphene-based nanostructures can serve as an appealing platform for optomechanical applications at the nanoscale. Here, we demonstrate, using full-wave simulations, the emergence of extremely strong bipolar optical forces, or, optical binding and anti-binding, between a pair of coupled graphene nanoribbons, due to the remarkable confinement and enhancement of optical fields arising from the large effective mode indices. In particular, the binding and anti-binding forces, which are about two orders of magnitude stronger than that in metamaterials and high-Q resonators, can be tailored by selective excitation of either the even or the odd optical modes, achievable by tuning the relative phase of the lightwaves propagating along the two ribbons. Based on the coupled mode theory, we derive analytical formulae for the bipolar optical forces, which agree well with the numerical results. The attractive optical binding force F(y)(b) and the repulsive anti-binding force F(y)(a) exhibit a remarkably different dependence on the gap distance g between the nanoribbons and the Fermi energy E(F), in the forms of F(y)(b) ∝ 1/√(g³E(F)) and F(y)(a) ∝ 1/E(F)(2). With E(F) dynamically tunable by bias voltage, the bipolar forces may provide a flexible handle for active control of the nanoscale optomechanical effects, and also, might be significant for optoelectronic and optothermal applications as well.
authors.affiliation: Department of Physics, China University of Mining and Technology, Xuzhou, Jiangsu 221116, China. luwl@cumt.edu.cn.
authors.forename: Wanli
authors.initials: W
authors.lastname: Lu
authors.affiliation: State Key Laboratory of Surface Physics and Department of Physics, Fudan University, Shanghai 200433, China. phlin@fudan.edu.cn and Key Laboratory of Micro and Nano Photonic Structures, Fudan University, Shanghai 200433, China.
authors.forename: Huajin
authors.initials: H
authors.lastname: Chen
authors.affiliation: State Key Laboratory of Surface Physics and Department of Physics, Fudan University, Shanghai 200433, China. phlin@fudan.edu.cn and Institute of Information Optics, Zhejiang Normal University, Jinhua, Zhejiang 321004, China. syliu@zjnu.cn.
authors.forename: Shiyang
authors.initials: S
authors.lastname: Liu
authors.affiliation: State Key Laboratory of Surface Physics and Department of Physics, Fudan University, Shanghai 200433, China. phlin@fudan.edu.cn and Key Laboratory of Micro and Nano Photonic Structures, Fudan University, Shanghai 200433, China.
authors.forename: Jian
authors.initials: J
authors.lastname: Zi
authors.affiliation: State Key Laboratory of Surface Physics and Department of Physics, Fudan University, Shanghai 200433, China. phlin@fudan.edu.cn and Key Laboratory of Micro and Nano Photonic Structures, Fudan University, Shanghai 200433, China and Collaborative Innovation Center of Advanced Microstructures, Fudan University, Shanghai 200433, China.
authors.forename: Zhifang
authors.initials: Z
authors.lastname: Lin