Electromagnetic scattering controlled all-dielectric cavity-antenna for bright, directional, and purely radiative single-photon emission

A deterministic, bright, room-temperature stable single-photon source (SPS) has been a major demand in the field of quantum photonics. Here, using computational and analytical techniques, we showed that the Mie-scattering moments of an all-dielectric cavity-cum-antenna help in shaping the spontaneous emission process of an embedded point-dipole emitter, the nanodiamond-based NV− and SiV color centers here. Our resonator-cum-antenna design comprises two top and bottom TiO2 cylinders with a sandwiched polyvinyl alcohol (PVA) layer enclosing the nanodiamond crystal. The Cartesian multi-polar decomposition of the Mie-scattering moments of the sandwiched PVA layer (enclosing the dipole emitter) with subwavelength scale thickness showed strong electric-dipole (ED) resonance. This resulted in significant field confinement, making the PVA layer to act as a cavity, providing a Purcell enhancement of more than an order of magnitude for all dipole orientations. The top and bottom TiO2 cylinders were observed to act as an antenna, and the far-field radiation pattern of the embedded dipole-emitter is controlled by the Mie-scattering moments of the TiO2 cylinders. The radiation directionality along the vertical directions was found to be maximum at the Kerker point (electric dipole moment, ED = magnetic dipole moment), the collection efficiency (CE) being about 80%. For dipole emission coupled to the antenna, the quantum efficiency was observed to increase to a high value of 0.98 for nanodiamond NV− center, very close to an ideal case of purely radiative emission. Our scheme is shown to be universal and can be applied to any solid-state-based quantum emitters, for generating on-demand SPS for quantum-photonic applications.