Ultrafast nonlinear photoresponse of single-wall carbon nanotubes: a broadband degenerate investigation

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 similar to 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.National Key Basic Research Program of China [2014CB921101]; National Natural Science Foundation of China [61378025, 61450110087, 61427812, 51522201, 11474006]; Jiangsu Province Shuang-chuang Team program; State Key Laboratory of Advanced Optical Communication Systems Networks, ChinaSCI(E)EIPubMedARTICLEfwang@nju.edu.cn; khliu@pku.edu.cn; ybxu@nju.edu.cn179304-9309