Exploiting one-dimensional exciton-phonon coupling for tunable and efficient single-photon generation with a carbon nanotube

TL;DR

This paper demonstrates how one-dimensional exciton-phonon coupling in carbon nanotubes can be exploited within tunable micro-cavities to produce highly efficient, spectrally pure single-photon sources with a broad tuning range, advancing quantum photonics.

Contribution

It introduces a novel method to utilize exciton-phonon interactions in carbon nanotubes for tunable, efficient single-photon emission in a cavity quantum electrodynamics setup.

Findings

Achieved a tuning range up to several hundred times the spectral width of the source.

Measured efficiency spectra in the Purcell regime for various mode volumes.

Observed spectrum deformation linked to exciton-photon coupling strength at different mode volumes.

Abstract

Condensed-matter emitters offer enriched cavity quantum electrodynamical effects due to the coupling to external degrees of freedom. In the case of carbon nanotubes a very peculiar coupling between localized excitons and the one-dimensional acoustic phonon modes can be achieved, which gives rise to pronounced phonon wings in the luminescence spectrum. By coupling an individual nanotube to a tunable optical micro-cavity, we show that this peculiar exciton-phonon coupling is a valuable resource to enlarge the tuning range of the single-photon source while keeping an excellent exciton-photon coupling efficiency and spectral purity. Using the unique flexibility of our scanning fiber cavity, we are able to measure the efficiency spectrum of the very same nanotube in the Purcell regime for several mode volumes. Whereas this efficiency spectrum looks very much like the free-space luminescence spectrum when the Purcell factor is small (large mode volume), we show that the deformation of this spectrum at lower mode volumes can be traced back to the strength of the exciton-photon coupling. It shows an enhanced efficiency on the red wing that arises from the asymmetry of the incoherent energy exchange processes between the exciton and the cavity. This allows us to obtain a tuning range up to several hundred times the spectral width of the source.