Speaker: Anton Malko
Title: Heralded Photons and Stimulated Emission Using Colloidal Semiconductor Quantum Shells
Abstract: Spherically shaped semiconductor nanoplatelets, called quantum shells (QSs) have recently attracted considerable attention as they exhibit strongly suppressed Auger recombination, ultralong biexciton (BX) lifetimes and broad gain bandwidth. However, no applications that demonstrate true lasing action using QSs in optical cavity configurations have been shown yet. Here, we design distributed feedback (DFB) cavities using lithographically defined SiO2 nanopillar arrays etched on Si substrates and filled with close-packed QS films. Using only one QSs size (i.e., confinement), we demonstrate emission coupling and narrowband lasing across a wide spectral range, from single exciton (X) to multiple exciton (MX) transitions. The record low lasing threshold results from almost completely impeded Auger recombination and low optical losses in the nanopillar cavity. Tuning of the lasing emission wavelength shows an excellent agreement with calculations as an array period is continuously varied, while maintaining the mode confinement and quality (Q) factors.
On the other hand, quantum information processing demands efficient quantum light sources (QLS) capable of producing high-fidelity single photons or entangled photon pairs. While colloidal semiconductor nanoparticles have long been thought for the purpose, they generally suffer from broader linewidths and unstable emissions. This leads to spectrally inseparable emissions from X and BX states, complicating the production of single photons and triggered photon pairs. We demonstrate that QSs achieve significant spectral separation (~ 75-80 meV) and long temporal stability, enabling the observation of BX-X bunching and emission of photon pairs for over 200 seconds, with minimal overlap between emissive features. The X-BX distinguishability allows for an in-depth theoretical characterization of cross-correlation strength, placing it in perspective with photon pairs of epitaxial counterparts.
