Cavity Quantum Electrodynamics with Carbon Nanotubes
Adrien Jeantet (LKB)

Carbon nanotubes are extensively investigated for their amazing mechanical
and electronic properties. Optically, they are excellent candidates for
on-demand single-photon sources because they can be electrically excited
and they can emit anti-bunched light at room temperature in the telecoms
bands. However, their emission efficiency is low, its origins remain
unclear and the spectral shape of their photoluminescence is complicated.
In this work, we build an original setup combining a confocal microscope
and a fiber based micro-cavity which is both spatially and spectrally
tunable. With this device, we observed the rise of cavity quantum
electrodynamics effects by analyzing the evolution of the dipole-cavity
coupling as a function of the cavity volume. We obtained a strong
acceleration of the spontaneous emission rate, due to Purcell factors
above 100. The associated effective efficiency of the source reaches up to
50%, leading to a brightness of up to 10%, while keeping excellent
anti-bunching features.
We observe the effect of the cavity coupling as a function of the cavity
detuning, and develop a model to account for emitters undergoing
exciton-phonon coupling in the presence of a cavity. We show that our
single-photon source is tunable on a range of frequencies more than a
hundred times higher than the cavity spectral width, opening the way to
extensive multiplexing.
Further strengthening of the coupling may open the way to the very rich
physics of one-dimensional cavity polaritons. And conversely, cavity
polaritons could be a tool to understand better the diffusion, and
localization properties of excitons in carbon nanotubes. Finally, the
original setup build here is extremely versatile and could be used to
coupled other types of emitters, such as nano-diamonds or molecules.