基于透明导电氧化物的表面等离激元电光调制技术研究

Optical interconnect is one of the important solutions meeting the increasing demand of data communication and processing. The ultracompact electro-optic modulator with low power consumption and large modulation depth is a key component of the optical interconnect system. In this project, we propose to study a surface plasmon polariton (SPP) modulator based on transparent conducting oxide (TCO). The SPP modulator consists of TCO whose electron density can be electrically tuned resulting in a large variation of the refractive index of the film, and a nano optical waveguide which has very strong electromagnetic field confinement due to the SPP effect. By optimizing the interaction between TCO and light in the nano optical waveguide, the electro-magnetic field can be highly confined into the carrier accumulation layer and therefore further improving the modulation of light transmission at low bias. We will study the mode properties of SPP mode considering the field localization and the propagation loss. Meanwhile, we will fabricate high quality TCO film and study its electrical modulation properties. We will study the device physics of various light modulation methods such as mode interference, phase and electro-absorption based on differently optimized SPP waveguides. We are also going to study the polarization dependence of the SPP modulation. And finally, we will fabricate one type of SPP ITO modulator and demonstrate its large modulation depth at low driving voltage. The research is believed to positively contribute to the development of photonic integration.

光互联是满足日益增长的信息传输与处理要求的重要途径之一，高集成度、低功耗和大调制深度的电光调制器是光互联的核心器件。本项目提出研究基于透明导电氧化物的表面等离激元(SPP)硅基光波导调制器。利用金属纳米光波导结构中SPP模式的高局域性和透明导电氧化物通过电调控其载流子分布可实现介电常数大幅改变的特点，构建金属纳米光波导与透明导电氧化物的复合光波导结构，实现高局域光模场与载流子积累层的强耦合，获得低偏压下的高效光传输调制。我们将研究SPP模式高局域和低损耗的光传输行为；研制高质量的透明导电氧化物薄膜并分析其电调制特性；针对不同复合结构对光波导模式有效折射率实部与虚部的调制效应，分别研究模式干涉型、相位型和电吸收型电光调制器件物理；针对SPP模式的单偏振选择性问题，研究偏振无关的SPP电光调制技术。并实验研制一种低功耗大调制深度的纳米光波导调制器。本项目成果对实现光互联和光子集成具有推动作用。

针对光电子集成技术对光调制器在尺寸、功耗、速度和性能方面不断提高的需求和新型等离子体激元（SPP）光调制技术研究的国际前沿问题，本项目深入研究强电磁场局域的SPP 波导结构和新型高灵敏电光材料ITO 结合的紧凑型可硅基集成的电光调制器。主要研究成果包括：（1）解决了SPP模式的单偏振选择性问题，提出了偏振无关的SPP光波导和超小型SPP波导偏振转换器；（2）研究了透明金属氧化物材料的载流子注入光调制特性和电控折射率近零的效应，并研制了10 nm超薄透明金属氧化物材料；（3）研究了基于折射率近零效应的电吸收型电光调制，并提出基于金属/绝缘体/ITO/绝缘体/硅的多层结构的双积累层SPP光波导调制器，理论调制效率高达10dB/μm，调制速度超过50GHz；（4）研究了偏振无关的光波导调制技术，提出偏振不灵敏SPP电光调制器，器件在两个偏振态下的消光比小于0.01dB/um。具体研究工作已发表四篇SCI论文，1次国外学术会议报告。