基于等离激元辅助隧穿效应的超快光电转换及技术研究

等离激元隧道结是指能同时支持表面等离激元和电子隧穿的金属-介质-金属纳米结构。基于等离激元辅助电子隧穿效应，利用纳米尺度隧道结可以实现超快光电转换，在超快光电探测等领域具有潜在应用价值。但是，由于隧道结中高度局域的等离激元模式与自由空间聚焦信号光之间存在显著的尺寸及模式失配，使得其光电转换效率低且难以与片上光波导集成，如何提高转换效率和集成度是目前需要解决的关键科学问题和技术难题。本项目提出了基于等离激元辅助隧穿效应的超快光电转换及技术研究设想。通过构建基于一维等离激元波导的新型传导型等离激元隧道结，探索利用强约束的导波模式取代自由空间聚焦形式实现信号光与隧道结的高效耦合，从而突破现有转换效率瓶颈。同时研究隧道结介质的功能化（如引入导电分子、整流分子等），进一步调控隧道结光电转换性能。研究结果对于传导型隧道结中光子、等离激元、隧穿电子相互作用及超快光电探测的研究和应用均具有重要意义。

A plasmonic tunnel junction is a metal-insulator-metal nanostructure that can simultaneously support surface plasmons and electron tunneling. Based on plasmon-assisted tunneling effect, plasmonic tunnel junctions can be used for the ultrafast conversion of photons into electrons, which is promising for applications such as ultrafast photodetection. However, the dramatic size and mode mismatch between highly localized plasmonic modes in a tunnel junction and the diffraction-limited focused light beam results in a low conversion efficiency and a difficulty in chip-scale integration of tunnel junctions with optical waveguides. These are the main issues and challenges faced in the area. In this project, we propose to investigate the ultrafast photoelectric conversion based on plasmon-assisted electron tunneling effect in plasmonic tunnel junctions. By constructing a propagating tunneling junctions based on one-dimentional plasmonic waveguides, we will investigate the use of highly confined propagating modes for the efficient excitation of a plasmonic tunnel junction instead of the use of focused light beam in free space, aiming to break the bottleneck of the conversion efficiency. At the same time, we will investigate the functionalization of tunnel junctions with functional materials including conductive molecules and molecules with a rectification function to further improve the photoelectric conversion performance. The outcome of this project is of great importance to the studies of the interaction of photon, plasmon, and tunneling electron in tunnel junctions and the application in ultrafast photodetections.