National Laboratory of Solid State Microstructures, Collaborative Innovation Center of Advanced Microstructures, Jiangsu Key Laboratory of Artificial Functional Materials, College of Engineering and Applied Sciences, Nanjing University, Nanjing, People's Republic of China.
State Key Lab for Mesoscopic Physics and School of Physics, Peking University, Beijing, People's Republic of China.
Nature. 2020 May;581(7809):401-405. doi: 10.1038/s41586-020-2306-9. Epub 2020 May 27.
Plasmonics enables the manipulation of light beyond the optical diffraction limit and may therefore confer advantages in applications such as photonic devices, optical cloaking, biochemical sensing and super-resolution imaging. However, the essential field-confinement capability of plasmonic devices is always accompanied by a parasitic Ohmic loss, which severely reduces their performance. Therefore, plasmonic materials (those with collective oscillations of electrons) with a lower loss than noble metals have long been sought. Here we present stable sodium-based plasmonic devices with state-of-the-art performance at near-infrared wavelengths. We fabricated high-quality sodium films with electron relaxation times as long as 0.42 picoseconds using a thermo-assisted spin-coating process. A direct-waveguide experiment shows that the propagation length of surface plasmon polaritons supported at the sodium-quartz interface can reach 200 micrometres at near-infrared wavelengths. We further demonstrate a room-temperature sodium-based plasmonic nanolaser with a lasing threshold of 140 kilowatts per square centimetre, lower than values previously reported for plasmonic nanolasers at near-infrared wavelengths. These sodium-based plasmonic devices show stable performance under ambient conditions over a period of several months after packaging with epoxy. These results indicate that the performance of plasmonic devices can be greatly improved beyond that of devices using noble metals, with implications for applications in plasmonics, nanophotonics and metamaterials.
等离子体激元学能够实现超越光学衍射极限的光操控，因此在光子器件、光学隐身、生化传感和超分辨率成像等应用中具有优势。然而，等离子体器件的基本场限制能力总是伴随着寄生的欧姆损耗，这严重降低了它们的性能。因此，长期以来，人们一直在寻找比贵金属具有更低损耗的等离子体材料（即具有电子集体振荡的材料）。在这里，我们展示了在近红外波长下具有最先进性能的稳定的基于钠的等离子体器件。我们使用热辅助旋涂工艺制造了高质量的钠膜，其电子弛豫时间长达 0.42 皮秒。直接波导实验表明，在钠-石英界面上支持的表面等离激元极化激元的传播长度在近红外波长下可达 200 微米。我们进一步展示了一种室温下基于钠的等离子体纳米激光器，其激光阈值为每平方厘米 140 千瓦，低于以前报道的近红外波长下的等离子体纳米激光器的阈值。这些基于钠的等离子体器件在封装环氧树脂后，在几个月的时间内能够在环境条件下保持稳定的性能。这些结果表明，等离子体器件的性能可以大大提高，超越使用贵金属的器件，这对于等离子体学、纳米光子学和超材料应用具有重要意义。
