Evidence for near-unity radiative quantum efficiency of bright excitons in carbon nanotubes from the Purcell effect

The efficiencies of photonic devices are primarily governed by radiative quantum efficiency, which is a property given by the light-emitting material. Quantitative characterization for carbon nanotubes, however, has been difficult despite being a prominent material for nanoscale photonics. Here we estimate the radiative quantum efficiency of bright excitons in carbon nanotubes by modifying the exciton dynamics through cavity quantum electrodynamical effects. Silicon photonic crystal nanobeam cavities are used to induce the Purcell effect on individual carbon nanotubes. Spectral and temporal behavior of the cavity enhancement is characterized by photoluminescence microscopy and the fraction of the radiative decay process is evaluated. We find that the radiative quantum efficiency can reach near unity for bright excitons in long air-suspended carbon nanotubes at room temperature.