Electrically Driven Quantum Dot Micropillar Light Sources

We report on light sources based on electrically pumped quantum dot (QD) micropillar cavities. The low-mode-volume high-quality microstructures feature pronounced cavity quantum electrodynamics (cQED) effects that are exploited for the realization of efficient single-photon sources and low-threshold microlasers. The compact and electrically driven devices are of special interest for applications in the field of quantum communication. In particular, operated as electrically triggered single-photon sources, the QD micropillars can act as building blocks for quantum key distribution and quantum repeaters. On the other hand, the electrically pumped microlasers with in-plane emission via whispering gallery modes or emission normal to the sample´s surface are predestinated for integrated light sources in future photonic networks. The devices are based on doped high-quality factor GaAs/AlAs microcavity structures with InGaAs QDs in the active layer. A lateral injection scheme leaves the upper facet of the micropillars free of any absorbing metal and allows for efficient light output under electrical pumping of low-mode-volume micropillars with diameters between 1 and 20 μm. Due to cQED effects, triggered single-photon emission with high photon extraction efficiency up to 62% and a low multiphoton emission probability (g⁽²⁾(0) = 0.16) are realized for moderate-quality (Q ) factor samples. The efficient coupling of spontaneous emission into the lasing mode in high- Q micropillars results in ultralow laser threshold currents of less than 10 μA at cryogenic temperatures. Our paper demonstrates the high potential of electrically driven QD micropillars to act as integrated light sources in future communication systems.