Boost of single-photon emission by perfect coupling of InAs/GaAs quantum dot and micropillar cavity mode

摘要

Quantum light source that emits single photons is the key device of quantum information processing [ – ]. High photon extraction efficiency, strong suppression of multi-photon emission, and high indistinguishability [ ] of the emitted single photons are desired. Among all the ways to realize quantum light sources such as atomic systems [ ], parametric down-conversion [ ], or vacancy centers in diamond [ , ], semiconductor InAs/GaAs quantum dots (QDs) are promising candidates to realize practical monolithic quantum light sources for quantum communication and other applications such as quantum-enhanced sensing [ ] or quantum imaging [ ]. The advantages of InAs/GaAs QDs include extremely narrow linewidth [ ], stable and on-demand emission with high single photon emission rate (can be enhanced by the cavity coupling) [ ], easy to tune through physical multi-fields [ – ], more suitable for fiber-array coupling output [ ], and the wavelength is tunable (840 ∼1300 nm at present) for potential telecom quantum information application [ ]. Despite its advantages, the key issue to realize a practical QD single-photon source is how to further improve the brightness (i.e., count rates) of single photon source, which will greatly improve the efficiency of quantum information transmission [ ]. Therefore, it is necessary to improve the extraction efficiency of QD emission and improve their brightness by means of coupling QDs with microcavities, including micropillars [ ], microdisk [ ], photonic crystals [ ], and microstructures like microlenses [ – ]. Meanwhile, the light-matter interaction of different systems and the coupling effect in the visible and infrared range have been extensively studied [ – ]. In recent years, the study of semiconductor QDs embedded in micropillar cavities and their cavity electrodynamic effects has attracted extensive attention for high value, low mode volume [ ], and its convenience in direct fiber-coupling output [ – ]. Furthermore, a perfect resonant coupling of the cavity mode with QD luminescence wavelength is another key challenge [ , ]. In this work, a pronounced crossover phenomenon of exciton energy and micropillar cavity mode (Q ∼ 3800) and an enhancement of exciton emission intensity were observed and an experimental precise cavity mode calibration process was proposed, which can achieve a perfect coupling of micropillar cavity mode and wavelength of QDs and then produce a single photon source with high brightness and high single-photon purity.