Nanophotonic Advances for Room-Temperature Single-Photon Sources

Abstract

This review reports on recent advances in room-temperature single-photon sources (SPSs) with photons exhibiting antibunching (separation of all photons in time in contrast to faint laser sources), including the authors’ results on SPSs with definite circular and linear polarizations. SPSs are important devices in secure quantum communication. Some quantum computing schemes are also based on such sources. Quantum metrology, quantum memory and fundamental physics experiments are other applications of SPSs. The critical issue in producing “antibunched” photons is the very low concentration of photon emitters, such that, within an excitation-laser focal spot, only one emitter becomes excited and which will emit only one photon at a time. Single “giant” colloidal semiconductor nanocrystal quantum dots and dot-in-rods, diamond color centers (both bulk and nanodiamonds), and trivalent rare-earth ions (TR3+) have the best photostability (longest operating time) in room-temperature excitation. This review is focused on nanophotonic aspects of the problem, describing room-temperature SPSs based on these emitters and some new stable single-emitters. We also describe methods for emitter fluorescence enhancement: microcavities (including photonic bandgap, Bragg reflector and chiral liquid crystal microcavities), plasmonic nanoantennas, and metamaterials. Finally, we describe the alignment of anisotropic single emitters with liquid crystals.