Department of Mechanical Engineering, Oakland University, Rochester, Michigan48309, United States.
Department of Physics, Michigan Technological University, Houghton, Michigan49931, United States.
Nano Lett. 2023 Jan 25;23(2):469-475. doi: 10.1021/acs.nanolett.2c03643. Epub 2023 Jan 11.
Sodium (Na) is predicted to be an ideal plasmonic material with ultralow optical loss across visible to near-infrared (NIR). However, there has been limited research on Na plasmonics. Here we develop a scalable fabrication method for Na nanostructures by combining phase-shift photolithography and a thermo-assisted spin-coating process. Using this method, we fabricated Na nanopit arrays with varying periodicities (300-600 nm) and with tunable surface plasmon polariton (SPP) modes spanning visible to NIR. We achieved SPP resonances as narrow as 9.3 nm. In addition, Na nanostructures showed line width narrowing from visible toward NIR, showing their prospect operating in the NIR. To address the challenges associated with the high reactivity of Na, we designed a simple encapsulation strategy and stabilized the Na nanostructures in ambient conditions for more than two months. As a low-cost and low-loss plasmonic material, Na offers a competitive option for nanophotonic devices and plasmon-enhanced applications.
钠（Na）被预测为一种理想的等离子体材料，在可见光到近红外（NIR）范围内具有超低的光学损耗。然而，关于 Na 等离子体的研究还很有限。在这里，我们通过结合相移光刻和热辅助旋涂工艺，开发了一种用于 Na 纳米结构的可扩展制造方法。使用这种方法，我们制造了具有不同周期性（300-600nm）的 Na 纳米孔阵列，并且可以调节表面等离子体激元（SPP）模式，覆盖可见光到 NIR。我们实现了窄至 9.3nm 的 SPP 共振。此外，Na 纳米结构在可见光到 NIR 方向表现出线宽变窄，表明它们有望在 NIR 波段工作。为了解决与 Na 的高反应性相关的挑战，我们设计了一种简单的封装策略，并在环境条件下将 Na 纳米结构稳定了两个多月。作为一种低成本、低损耗的等离子体材料，Na 为纳米光子器件和等离子体增强应用提供了一种有竞争力的选择。
