Spontaneous photon-pair generation from a dielectric nanoantenna

Abstract

Optical nanoantennas have shown a great capacity for efficient extraction of\nphotons from the near to the far-field, enabling directional emission from\nnanoscale single-photon sources. However, their potential for the generation\nand extraction of multi-photon quantum states remains unexplored. Here we\ndemonstrate experimentally the nanoscale generation of two-photon quantum\nstates at telecommunication wavelengths based on spontaneous parametric\ndown-conversion in an optical nanoantenna. The antenna is a crystalline AlGaAs\nnanocylinder, possessing Mie-type resonances at both the pump and the bi-photon\nwavelengths and when excited by a pump beam generates photonpairs with a rate\nof 35 Hz. Normalized to the pump energy stored by the nanoantenna, this rate\ncorresponds to 1.4 GHz/Wm, being one order of magnitude higher than\nconventional on-chip or bulk photon-pair sources. Our experiments open the way\nfor multiplexing several antennas for coherent generation of multi-photon\nquantum states with complex spatial-mode entanglement and applications in\nfree-space quantum communications and sensing.\n