Vice-professor Ying Gu and Academician Qihuang Gong et al. in Peking University “State Key Laboratory For Artificial Microstructure and Mesoscopic physics” theoretically demonstrated efficient single photon emission and one-dimensional low-loss nanoscale guiding by putting quantum emitter into the nanoscale gap formed by metallic nanorod and nanofilm. This result was published in Physical Review Letters in 15th of May, 2015. (Efficient Single Photon Emission and Collection Based on Excitation of Gap Surface Plasmons，PRL 114, 193002 (2015)).The first author is a second-year PHD student Hang Lian, and the corresponding author is vice-professor Ying Gu.

Single photon emission is of fundamental interest for research in cavity quantum electrodynamics (CQED), single photon sources, and cavity-based lasing processes. Based on the principle of the Purcell effect, the spontaneous emission rates can be enhanced by the modification of the density of states of the electromagnetic field. To meet the requirements of on-chip optics, various nanophotonic structures have been proposed to tailor the emission rates, but with the drawback of inadequate enhancement of spontaneous emission rates. Plasmonic structures have been considered to improve on that situation, specially, gap plasmon structures are proposed as excellent candidates since they can provide large spontaneous emission enhancement.

By combining the advantages of ultrahigh emission rates in gap plasmon system with high extraction into low-loss nanofibers, they theoretically demonstrate the efficient emission and one-dimensional nanoscale guiding in metallic nanorod-coupled nanofilm structures coupled to dielectric nanofibers. They find the total decay rates and surface plasmon polariton channel decay rates orders of magnitude larger than those characteristic of metallic nanofilms alone can be achieved in ultrastrong hot spots of gap plasmons. For the requirement of practical applications, propagating single photons with decay rates of290γ0–770γ0 are guided into the phase-matched low-loss nanofibers. The proposed mechanism promises to have an important impact on metal-based optical cavities, on-chip bright single photon sources and plasmon-based nanolasers.

This work was supported by the National Natural Science Foundation of China “the Major Program”and“Innovative Research Groups”, by the National Key Basic Research Program “973 project”, and by the support of Peking University “State Key Laboratory For Artificial Microstructure and Mesoscopic physics”.

Related links:http://dx.doi.org/10.1103/PhysRevLett.114.193002