"Dark" and "Bright" Excitons in Carbon Nanotubes: New Media for Quantum Optics

It is well-known that strong Coulomb effects in carbon nanotubes lead to formation of the so-called "bright" and "dark" (forbidden one-photon optical transition) exciton states, and dramatically decrease the efficiency of one-photon light emission via trapping of the carriers by "dark" states. We suggest and demonstrate that the proper use of these "bright" and "dark" exciton states with distinctively different recombination times may turn the situation around: the use of quantum coherence and multiphoton schemes of excitation potentially not only allow one to efficiently manipulate the dark states, but can also create conditions for efficient light generation in different frequency regions, produce "slow" or "fast" light, implement quantum light storage, and media with a negative refractive index. We discuss possible applications of the quantum coherent effects to quantum-optical carbon nanotube devices that have a potential for suitable performance at elevated temperatures, because the binding energies of excitons in single-walled nanotubes are hundreds-of-meV high