Circularly polarized cavity-mode emission from quantum dots in a semiconductor three-dimensional chiral photonic crystal

We experimentally demonstrated a circularly polarized cavity mode in a GaAs-based chiral photonic crystal (PhC) containing a planar defect. Low-temperature photoluminescence measurements of InAs quantum dots (QDs) embedded in the planar defect revealed a polarization bandgap for left-handed circularly polarized light in the near-infrared spectrum. Within this bandgap, where the QDs preferably emitted right-handed circularly polarized light, we observed a distinct cavity-mode peak characterized by left-handed circular polarization. This observation indicates that the chiral PhC modifies the optical density of states for left-handed circular polarization to be suppressed in the polarization bandgap and be largely enhanced at the cavity mode. The results obtained may not only provide photonic devices such as compact circularly polarized light sources but also promote strong coupling between circularly polarized photons and excitons in solid states or molecules, paving the way for advancements in polaritonics, spintronics, and quantum information technology.