A controlled light source has been developed that is based on a nanodiamond. According to researchers, experiments showed that the diamond shell could double the emission speed of light sources and could help control light sources without additional nano- or microstructures. The enhancement of the fluorescence rate of the emitters was due to artificially created defects in a diamond crystal lattice. Nanodiamonds with artificially created nitrogen-vacancy centers (NV centers) were used for the nanoantennas. Schematic of active nanodiamond antenna. Courtesy of ITMO University. The ITMO University research team, in collaboration with researchers from Australian National University, made the NV centers by removing carbon atoms from a diamond crystal lattice. They then linked each NV center to an implanted nitrogen atom. Researchers found that the electron spin of such an NV center could be easily controlled by light. In a theoretical study of the optical properties of nanodiamond antennas, including the field enhancement and Purcell effect, the team found that the radiation of nanodiamond antennas could be enhanced by combining the NV center luminescence spectrum with optical Mie resonances of diamond nanoparticles, at a certain position of the NV center and at the appropriate particle size. Using this approach, researchers were able to increase the Purcell factor, an indicator that can be used to estimate how a diamond shell affects the rate of spontaneous emission of the light source. If the Purcell factor increases, the luminescence fading time is reduced, and the signal becomes stronger and easier to read. The team achieved this effect using nanodiamonds only. “Usually, to accelerate the radiation, one has to create a complex system of resonators,” said researcher Dmitry Zuev. “But we managed to achieve similar results without any additional structures. We showed experimentally that the luminescence fading can be speeded up at least two times, using just simple physics.” Researchers also developed a theoretical model for the behavior of single-photon sources in the diamond shell. Calculations showed that the speed of light emission could be increased by several dozen times. “Today, getting a single photon from one NV center in a nanoantenna is a rather difficult task,” said researcher Anastasia Zalogina. “In order to implement such an active nanoantenna in logic elements, for example, you need to manage their emission. In perspective, our concept will help to effectively manage single-photon emission sources. It is very important for the development of quantum computers and optical communication networks.” Typically, plasmonic metal nanoparticles are used as a base for nanoantennas, but these nanoparticles can experience optical loss. A search for alternatives is what led the research team to develop active dielectric nanoantennas based on nanodiamonds. Researchers noted that nanodiamonds have properties that make them suitable for use as a nanoantenna base, including a high refractive index, high thermal conductivity, and low interaction activity. Results of this research could help pave the way toward active dielectric nanophotonics for quantum light sources, bioimaging, and quantum information processing. The research was published in Nanoscale (doi: 10.1039/C7NR07953B).