Gate-variable light absorption and emission in a semiconducting carbon nanotube

We investigate the gate field dependence of light absorption and emission of an individual, suspended semiconducting carbon nanotube using Raman and photoluminescence spectroscopies. We find a strong reduction in the absorption strength and a red shift of the E₃₃ state of the nanotube with increasing gate field. The photoluminescence from the E₁₁ state Is quenched even stronger. We explain these observations in terms of field-doping and Its effects on both the radiative and nonradiatlve decay rates of the excitons. Thus, gate field-induced doping constitutes an effective means of controlling the optical properties of carbon nanotube devices.