Figure 1.

(a) Visual abstract of the fluorescent single photon emission of semiconductor QDs. Above-band excitation promotes an electron to the conduction band, from where it non-radiatively relaxes to the s-shell in the QD. The electron subsequently recombines with the electron hole left behind in the valence band and thereby emits a single photon with the energy of the QD state. (b) Schematic spectrum of the excitation laser (dark blue) and the QD emission (light blue). (c) Schematic side view of a $\text{InAs/GaAs}$ QD sample formed through epitaxial self-assembly.