Laser switching characteristics of enriched (7,5) single-walled carbon nanotubes at 640 nm.

Single-walled carbon nanotubes (SWCNTs) with a narrow diameter or chirality distribution have great potential in promoting carbon nanophotonics and nanoelectronics. In this paper, SWCNTs with dominant (7,5) species, which are fabricated by chemical vapor deposition method from a magnesia-supported Co catalyst, are applied for the nonlinear optical measurements. The SWCNTs exhibit efficient saturable absorption properties at a wavelength of 640 nm in terms of a modulation depth of 27.7% and a saturable intensity of 5.7 GW/cm2. Such a 640 nm absorption is correlated with the S 22 absorbance bands of the semiconducting SWCNTs. Consequently, by employing the SWCNTs as a saturable absorber (SA), stable Q-switched pulses with the shortest pulse width of 200 ns and maximum pulse repetition rate of 238 kHz are achieved at 640 nm. Our findings indicate that subnanometer semiconducting SWCNT could act as an excellent optical switcher device at 640 nm, which may help to explore potential applications in visible nonlinear optics. The fitting results of the modulation depth and saturable intensity are determined to be 27.7% and 5.7 GW/cm2, respectively. The relative larger modulation depth originating from uniform diameter distribution of the SWCNTs is conductive to generate shorter laser pulse. [Display omitted] [ABSTRACT FROM AUTHOR]