The dephasing and population decay dynamics of optical phonons are studied for semiconducting single-wall carbon nanotubes (SWCNTs) using broadband time-resolved coherent anti-Stokes Raman scattering (TR-CARS) and time-resolved incoherent anti-Stokes Raman scattering (TR-IARS). By simply adjusting the spectral bandwidth of a continuum pulse, we are able to measure the total dephasing time, T2, and the population decay time, T1, of the G-band sequentially in the same sample. For two different SWCNT samples (bundles on glass and isolated dispersion in water), T2/2 is measured to be shorter than T1. Assuming that inhomogeneous broadening is small, the T2/2 and T1 measurements at the identical sample regions are used to determine the pure dephasing time, T2*/2. The determined pure dephasing time is faster in bundled SWCNTs than in isolated dispersion, suggesting stronger perturbation by neighboring tubes than by surfactants.
Citation: Nano Letters
Pub Type: Journals
Coherent anti-Stokes Raman scattering, phonon dynamics, dephasing time, population decay, single wall carbon nanotubes