Generating single photons at GHz modulation-speed using electrically controlled quantum dot microlenses

Abstract

We report on the generation of single-photon pulse trains at a repetition rate of up to 1 GHz. We achieve this high speed by modulating the external voltage applied on an electrically contacted quantum dot microlens, which is optically excited by a continuous-wave laser. By modulating the photoluminescence of the quantum dot microlens using a square-wave voltage, single-photon emission is triggered with a response time as short as 270 ps being 6.5 times faster than the radiative lifetime of 1.75 ns. This large reduction in the characteristic emission time is enabled by a rapid capacitive gating of emission from the quantum dot placed in the intrinsic region of a p-i-n-junction biased below the onset of electroluminescence. Here, the rising edge of the applied voltage pulses triggers the emission of single photons from the optically excited quantum dot. The non-classical nature of the photon pulse train generated at GHz-speed is proven by intensity autocorrelation measurements. Our results combine optical excitation with fast electrical gating and thus show promise for the generation of indistinguishable single photons at high rates, exceeding the limitations set by the intrinsic radiative lifetime.