RESUMEN
Using predesigned trains of femtosecond optical pulses, we have selectively excited coherent phonons of the radial breathing mode of specific-chirality single-walled carbon nanotubes within an ensemble sample. By analyzing the initial phase of the phonon oscillations, we prove that the tube diameter initially increases in response to ultrafast photoexcitation. Furthermore, from excitation profiles, we demonstrate that an excitonic absorption peak of carbon nanotubes periodically oscillates as a function of time when the tube diameter undergoes coherent radial breathing mode oscillations.
RESUMEN
Two phase-locked pulses are used to coherently excite excitonic polarizations. It is shown that the second pulse can either be strongly amplified by taking up energy gained from the destruction of the exciton polarization or can be decreased drastically by giving up all its energy to excitons. Both the temporal and the spectral signatures of the transmitted pulse shapes agree well with model calculations.