  We have observed large-amplitude coherent phonon oscillations of radial
breathing modes (RBMs) in single-walled carbon nanotubes excited through the
lowest-energy (E11) interband transitions. In contrast to the
previously-studied coherent phonons excited through higher-energy (E22)
transitions, these RBMs show comparable intensities between (n-m) mod 3 = 1 and
-1 nanotubes. We also find novel non-resonantly excited RBMs over an excitation
range of ~300 meV above the E11 transition, which we attribute to multi-phonon
replicas arising from strong exciton-phonon coupling.
