基于电子隧穿效应的传导型等离激元激发研究

传导型表面等离极化激元（SPP）的产生通常采用受衍射极限限制的光学激发方式，极大限制了等离激元器件的小型化及片上高密度集成。利用隧道结内电子隧穿效应可以实现等离激元的高速、超紧凑电激发。但是，传统金属-介质-金属隧道结内高度局域的等离激元模式具有高传播常数、高传输损耗特性，使得其与金属波导中传导型SPP之间的耦合效率极低，极大限制了电激发SPP的输出功率（皮瓦量级或更低）。本项目提出了基于电子隧穿效应的传导型等离激元激发研究设想，拟在金属波导上构建石墨烯-介质-金纳米颗粒隧道结阵列，利用电子隧穿效应直接激发金纳米颗粒阵列等离激元模式，通过调控该模式与SPP的模式匹配，实现两者间的高效耦合，从而有效提高输出功率。同时，通过调控隧道结阵列的光学响应，可以进一步实现电激发SPP光谱的有效调控。研究结果对于隧道结等离激元模式与SPP耦合及电激发等离激元器件的研究和应用均具有重要意义。

Usually, surface plasmon polaritons (SPPs) are excited by diffraction-limited optical methods, which greatly limit the miniaturization and high-density integration of plasmonic devices. By using electron tunneling effect in a plasmonic tunnel junction, surface plasmons can be electrically excited with advantages including ultra-fast speed and ultra-small footprint. However, due to the large propagation constant and propagation loss of the highly confined plasmonic mode in a metal-insulator-metal junction, the coupling efficiency between the confined plasmonic mode and the SPP mode in a waveguide is quite low, resulting in a limited output power from the excited SPP (pW level or lower). In this project, we propose to study the electrical excitation of propagating SPPs based electron tunneling effect. We will construct grapheme-insulator-gold nanoparticle tunnel junction array directly on a plasmonic waveguide. By exciting the plasmonic modes of the gold nanoparticle array directly with tunneling electrons and optimizing their mode matching with the SPP mode in the waveguide, we aim to realize their efficient coupling and thus greatly improve the output power. Meanwhile, by tuning the optical response of the nanoparticle array, we aim to control the spectrum of the electrically-excited SPP. The outcome of this project is of great importance to the studies of efficient coupling between plasmonic modes of a tunnel junction and SPP modes and applications of electrically-driven plasmonic devices.