title: Ultrafast nonlinear photoresponse of single-wall carbon nanotubes: a broadband degenerate investigation.
abstract: Understanding of the fundamental photoresponse of carbon nanotubes has broad implications for various photonic and optoelectronic devices. Here, Z-scan and pump-probe spectroscopy performed across 600-2400 nm were combined to give a broadband 'degenerate' mapping of the nonlinear absorption properties of single-wall carbon nanotubes (SWNTs). In contrast to the views obtained from non-degenerate techniques, sizable saturable absorption is observed from the visible to the near-infrared range, including the spectral regions between semiconducting excitonic peaks and metallic tube transitions. In addition, the broadband mapping unambiguously reveals a photobleaching to photoinduced absorption transition feature within the first semiconducting excitonic band ∼2100 nm, quantitatively marking the long-wavelength cut-off for saturable absorption of the SWNTs investigated. Our findings present a much clearer physical picture of SWNTs' nonlinear absorption characteristics, and help provide updated design guidelines for SWNT based nonlinear optical devices.
authors.affiliation: School of Electronic Science and Engineering and Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing 210093, China. fwang@nju.edu.cn ybxu@nju.edu.cn.
authors.forename: Shuo
authors.initials: S
authors.lastname: Xu
authors.affiliation: School of Electronic Science and Engineering and Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing 210093, China. fwang@nju.edu.cn ybxu@nju.edu.cn.
authors.forename: Fengqiu
authors.initials: F
authors.lastname: Wang
authors.affiliation: School of Electronic Science and Engineering and Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing 210093, China. fwang@nju.edu.cn ybxu@nju.edu.cn.
authors.forename: Chunhui
authors.initials: C
authors.lastname: Zhu
authors.affiliation: School of Electronic Science and Engineering and Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing 210093, China. fwang@nju.edu.cn ybxu@nju.edu.cn.
authors.forename: Yafei
authors.initials: Y
authors.lastname: Meng
authors.affiliation: School of Electronic Science and Engineering and Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing 210093, China. fwang@nju.edu.cn ybxu@nju.edu.cn.
authors.forename: Yujie
authors.initials: Y
authors.lastname: Liu
authors.affiliation: School of Electronic Science and Engineering and Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing 210093, China. fwang@nju.edu.cn ybxu@nju.edu.cn.
authors.forename: Wenqing
authors.initials: W
authors.lastname: Liu
authors.affiliation: State Key Laboratory for Mesoscopic Physics, School of Physics and Collaborative Innovation Center of Quantum Matter, Peking University, Beijing 100871, China. khliu@pku.edu.cn.
authors.forename: Jingyi
authors.initials: J
authors.lastname: Tang
authors.affiliation: State Key Laboratory for Mesoscopic Physics, School of Physics and Collaborative Innovation Center of Quantum Matter, Peking University, Beijing 100871, China. khliu@pku.edu.cn.
authors.forename: Kaihui
authors.initials: K
authors.lastname: Liu
authors.affiliation: Cambridge Graphene Centre, University of Cambridge, Cambridge CB3 0FA, UK.
authors.forename: Guohua
authors.initials: G
authors.lastname: Hu
authors.affiliation: Cambridge Graphene Centre, University of Cambridge, Cambridge CB3 0FA, UK.
authors.forename: Richard C T
authors.initials: RC
authors.lastname: Howe
authors.affiliation: Cambridge Graphene Centre, University of Cambridge, Cambridge CB3 0FA, UK.
authors.forename: Tawfique
authors.initials: T
authors.lastname: Hasan
authors.affiliation: School of Electronic Science and Engineering and Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing 210093, China. fwang@nju.edu.cn ybxu@nju.edu.cn.
authors.forename: Rong
authors.initials: R
authors.lastname: Zhang
authors.affiliation: School of Electronic Science and Engineering and Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing 210093, China. fwang@nju.edu.cn ybxu@nju.edu.cn.
authors.forename: Yi
authors.initials: Y
authors.lastname: Shi
authors.affiliation: School of Electronic Science and Engineering and Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing 210093, China. fwang@nju.edu.cn ybxu@nju.edu.cn.
authors.forename: Yongbing
authors.initials: Y
authors.lastname: Xu