We show that strong light-matter coupling can be used to overcome a long
standing problem that has prevented efficient optical emission from carbon
nanotubes. The luminescence from the nominally bright exciton states of carbon
nanotubes is quenched due to the fast nonradiative scattering to the dark
exciton state having a lower energy. We present a theoretical analysis to show
that by placing carbon nanotubes in an optical microcavity the bright exctonic
state may be split into two hybrid exciton-polariton states, while the dark
state remains unaltered. For sufficiently strong coupling between the bright
exciton and the cavity, we show that the energy of the lower polariton may be
pushed below that of the dark exciton. This overturning of the relative
energies of the bright and dark excitons prevents the dark exciton from
quenching the emission. Our resutls pave the way for a new approach to
band-engineering the properties of the nanoscale optoelectronic devices.Comment: 35 pages, 5 figures, 6 pages of supplementary materials, 1
supplementary figur