Quantum emitters coupled to circular nanoantennas for high-brightness quantum light sources

Engineering the directionality and emission rate of quantum light sources is essential in the development of modern quantumapplications. In this work we use numerical calculations to optimise the brightness of a broadband quantumemitter positioned in a hybridmetal-dielectric circular periodic nanoantenna. The optimised structure features a photon collection efficiency of 74% (82%) and a photon flux enhancement of over 10 (6) into a numerical aperture of 0.22 (0.50), respectively, corresponding to a direct coupling into two types ofmulti-mode fibres.To enhance the emission rate, we present a new circular nanoantenna design where a quantum emitter is attached to a silver nanocone at the centre of the antenna.After optimisation,we find a collection efficiency of 61% (78%) into a numerical aperture of 0.22 (0.50), giving a brightness enhancement of 1000 (600) for an unpolarised emitter. The enhancements in both structures are broadband due to the low-quality factor of the device and are therefore ideal for room-temperature sources. This type of a scalable design can be utilised towards on-chip, high-brightness quantum light sources operating at roomtemperature.