Bright Polarized Single-Photon Source Based on a Linear Dipole
Résumé
Semiconductor quantum dots in cavities have emerged as high-performance single-photon sources for quantum technologies. However, they are still far from ideal deterministic operation, which simultaneously requires perfect linear polarization, population inversion and collection efficiency. Thus far, the best performing sources have used an unpolarized emitter together with polarized photon extraction. Here, we explore a new path to deterministic operation: exploiting the natural asymmetry of neutral quantum dots that present linearly-polarized dipoles and allow for the emission of fully polarized light. To benefit from such a property, we propose the use of off-resonant phonon-assisted excitation that has been theoretically predicted to enable near-unity population inversion and quantum purity. We experimentally study this approach for quantum dots in micropillar cavities and demonstrate single-photon emission with a degree of linear polarization up to 0.994 $\pm$ 0.007 and a high population inversion -- 85\% as high as resonant excitation. We demonstrate a single-photon source with a polarized first lens brightness of 0.51 $\pm $ 0.01, a single-photon purity of 0.939 $\pm$ 0.001 and single-photon indistinguishability of 0.915 $\pm$ 0.003.
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