Session 9-5

Abstract

In this talk, we explore recent advancements in photon upconversion and quantum light source development using single-walled carbon nanotubes (SWNTs). We first investigate the intrinsic microscopic mechanisms of photon upconversion in air-suspended SWNTs via photoluminescence and upconversion spectroscopy. A nearly linear excitation power dependence of upconversion photoluminescence intensity suggests a one-photon process as the underlying mechanism. Additionally, the strongly anisotropic response to excitation polarization reveals the intrinsic nature of this process. Upconversion photoluminescence excitation spectra show three peaks, similar to the photoluminescence sidebands of the K-momentum dark singlet exciton. These are well-explained by our exciton-phonon interaction model, which determines phonon energies and relative amplitudes, indicating upconversion as a reverse process of sideband emission linked to K-momentum phonon modes. Temperature-dependent measurements further support this model, emphasizing the role of resonant exciton-phonon coupling in SWNTs and its potential for advanced optothermal technologies and biosensing [2].
Transitioning to quantum light sources, SWNTs offer a promising platform due to their unique optical properties, but controlled introduction of quantum defects remains a challenge. We address this by developing an in-situ photochemical reactor for precise defect introduction in air-suspended SWNTs, allowing reaction halting at the initial emergence of defect emission [3]. This leads to a controlled increase in photoluminescence intensity and reveals a preference for E11− emitters with spatially controlled defect sites. We demonstrate single-photon emission from these defects, marking a step toward precision-engineered quantum light sources. This fine control over defect formation advances the field closer to practical quantum information systems and room-temperature operable quantum photonic circuits.