Photonics Laboratory, ETH Zürich, Zürich 8093, Switzerland.
National Institute for Material Science, 1-1 Namiki, Tsukuba 305-0044, Japan.
Nat Nanotechnol. 2015 Dec;10(12):1058-63. doi: 10.1038/nnano.2015.203. Epub 2015 Sep 14.
The ultrafast conversion of electrical signals to optical signals at the nanoscale is of fundamental interest for data processing, telecommunication and optical interconnects. However, the modulation bandwidths of semiconductor light-emitting diodes are limited by the spontaneous recombination rate of electron-hole pairs, and the footprint of electrically driven ultrafast lasers is too large for practical on-chip integration. A metal-insulator-metal tunnel junction approaches the ultimate size limit of electronic devices and its operating speed is fundamentally limited only by the tunnelling time. Here, we study the conversion of electrons (localized in vertical gold-hexagonal boron nitride-gold tunnel junctions) to free-space photons, mediated by resonant slot antennas. Optical antennas efficiently bridge the size mismatch between nanoscale volumes and far-field radiation and strongly enhance the electron-photon conversion efficiency. We achieve polarized, directional and resonantly enhanced light emission from inelastic electron tunnelling and establish a novel platform for studying the interaction of electrons with strongly localized electromagnetic fields.
在纳米尺度上，将电信号超快地转换为光信号，这对于数据处理、电信和光互连都具有重要的意义。然而，半导体发光二极管的调制带宽受到电子-空穴对的自发复合率的限制，而电驱动的超快激光器的尺寸太大，不适合实际的片上集成。金属-绝缘体-金属隧道结接近电子器件的极限尺寸，其工作速度仅受隧道时间的限制。在这里，我们研究了通过共振缝隙天线介导的电子（局域在垂直的金-六方氮化硼-金隧道结中）到自由空间光子的转换。光学天线有效地桥接了纳米体积与远场辐射之间的尺寸不匹配，并强烈增强了电子-光子转换效率。我们实现了非弹性电子隧穿的偏振、定向和共振增强发光，并建立了一个研究电子与强局域电磁场相互作用的新平台。
