Department of Materials Science and Engineering, University of Pennsylvania, Philadelphia, Pennsylvania 19104, USA.
Nat Mater. 2011 Jul 17;10(9):669-75. doi: 10.1038/nmat3067.
The manipulation of radiative properties of light emitters coupled with surface plasmons is important for engineering new nanoscale optoelectronic devices, including lasers, detectors and single photon emitters. However, so far the radiative rates of excited states in semiconductors and molecular systems have been enhanced only moderately, typically by a factor of 10-50, producing emission mostly from thermalized excitons. Here, we show the generation of dominant hot-exciton emission, that is, luminescence from non-thermalized excitons that are enhanced by the highly concentrated electromagnetic fields supported by the resonant whispering-gallery plasmonic nanocavities of CdS-SiO(2)-Ag core-shell nanowire devices. By tuning the plasmonic cavity size to match the whispering-gallery resonances, an almost complete transition from thermalized exciton to hot-exciton emission can be achieved, which reflects exceptionally high radiative rate enhancement of >10(3) and sub-picosecond lifetimes. Core-shell plasmonic nanowires are an ideal test bed for studying and controlling strong plasmon-exciton interaction at the nanoscale and opens new avenues for applications in ultrafast nanophotonic devices.
与表面等离激元耦合的光发射器的辐射性质的操纵对于工程新的纳米级光电设备，包括激光、探测器和单光子发射器，非常重要。然而，到目前为止，半导体和分子系统中激发态的辐射率仅适度提高，通常提高因子为 10-50，主要产生来自热化激子的发射。在这里，我们展示了主要的热激子发射的产生，即由 CdS-SiO(2)-Ag 核壳纳米线器件的共振 whispering-gallery 等离子体纳米腔所支持的高度集中的电磁场增强的非热化激子的发光。通过调整等离子体腔的大小以匹配 whispering-gallery 共振，可以实现从热化激子到热激子发射的几乎完全转变，这反映了异常高的 >10(3)的辐射率增强和亚皮秒寿命。核壳等离子体纳米线是研究和控制纳米尺度上强等离子激元-激子相互作用的理想试验台，并为超快纳米光子器件的应用开辟了新途径。
