Population of Exciton-Polaritons via Luminescent sp$^{3}$ Defects in Single-Walled Carbon Nanotubes

Abstract

Semiconducting single-walled carbon-nanotubes (SWCNTs) are an interesting material for strong-light matter coupling due to their stable excitons, narrow emission in the near infrared and high charge carrier mobilities. Furthermore, they have emerged as quantum light sources as a result of the controlled introduction of luminescent quantum defects (sp$^{3}$-defects) with red-shifted transitions that enable single-photon emission. The complex photophysics of SWCNTs and overall goal of polariton condensation pose the question of how exciton-polaritons are populated and how it might be optimized. The contributions of possible relaxation processes, i.e., scattering with acoustic phonons, vibrationally assisted scattering, and radiative pumping, are investigated using angle-resolved reflectivity and time-resolved photoluminescence measurements on microcavities with a wide range of detunings. We show that the predominant population mechanism for SWCNT exciton-polaritons in planar microcavities is radiative pumping. Consequently, the limitation of polariton population due to the low photoluminescence quantum yield of nanotubes, can be overcome by luminescent sp$^{3}$ defects. Without changing the polariton branch structure, radiative pumping through these emissive defects leads to an up to 10-fold increase of the polariton population for detunings with a large photon fraction. Thus, the controlled and tunable functionalization of SWCNTs with sp$^{3}$ defects presents a viable route towards bright and efficient polariton devices.