Lifetime Measurements Well below the Optical Diffraction Limit

The dependence of excited electron hole state properties on the size of their host semiconducting nanostructures is the seed for a plethora of applications such as light-emitting diodes (LEDs) and photovoltaic cells. However, the inability of state-of-the art, diffraction limited optical techniques to probe lifetime variations at the scale of individual quantum emitters precludes the full understanding of the nanostructures' optical properties. Here, we demonstrate the measurement of the individual lifetimes of quantum emitters a few angstroms thick separated by only a few nanometers, lifting the ambiguities usually faced by diffraction-limited techniques. This relies on the ability to monitor with subnanometer precision a fast electron beam that triggers extremely localized cathodoluminescence signals further analyzed through intensity interferometry (spatially resolved time-correlated cathodoluminescence, SRTC-CL). We demonstrate SRTC-CL to be a true nanometer counterpart of time-resolved photoluminescence, opening the way for a deeper understanding of suboptical wavelength objects such as biomarkers, quantum heterostructures, active parts of LEDs, or quantum optics devices.