Narrow optical linewidths and spin pumping on charge-tunable, close-to-surface self-assembled quantum dots in an ultra-thin diode
Abstract
We demonstrate full charge control, narrow optical linewidths, and optical spin pumping on single self-assembled InGaAs quantum dots embedded in a 162.5\,nm thin diode structure. The quantum dots are just 88\,nm from the top GaAs surface. We design and realize a p-i-n-i-n diode that allows single-electron charging of the quantum dots at close-to-zero applied bias. In operation, the current flow through the device is extremely small resulting in low noise. In resonance fluorescence, we measure optical linewidths below 2\,μeV, just a factor of two above the transform limit. Clear optical spin pumping is observed in a magnetic field of 0.5\,T in the Faraday geometry. We present this design as ideal for securing the advantages of self-assembled quantum dots -- highly coherent single photon generation, ultra-fast optical spin manipulation -- in the thin diodes required in quantum nano-photonics and nano-phononics applications.