基于硫系相变材料的非易失性硅基集成光开关阵列芯片研究

Silicon optical matrix switch chips for reconfigurable optical signal routing from any input port to any output port, are one of the most fundamental and critical components in optical switch networks. Current on-chip silicon optical switches based on electro-optic or thermo-optic effects produce small refractive index perturbations with volatile nature and the alternatives of the optical switch unit is limited. To alleviate these issues, the project proposed to exploit the characteristics of the non-volatile and high optical contrast of phase change material and the planar bridge waveguide coupler to obtain a non-perturbative and non-volatile silicon optical switch unit, then implementing the optical matrix chip through the switch topology. This project focuses at two key scientific issues: the non-perturbative regulatory mechanism and the working mechanism of 2×2 optical switch based on the hybrid waveguide. In this project, a high figure-of-merit phase change material, optical property based on hybrid GSST-on-silicon waveguide, the optical switch unit based on planar bridge waveguide coupler and the 8×8 optical matrix switch will be investigated. Through aiming at clarifying the non-perturbative regulatory mechanism of the hybrid waveguide, and resolving the key technology of the 2×2 optical switch unit with high performance, the project will provide an non-volatile silicon integrated optical matrix switch chip based on phase-change material with low insertion loss(~6dB), low cross talk(<-25dB) and wide band(~30nm), and lay a solid scientific foundation for the application in optical interconnection, field-programmable reconfigurable photonics and other research fields.

光开关阵列芯片能够将任意端口输入的光信号从任意端口输出，是片上光互连网络中最基础、最核心器件之一。针对现有硅基光开关阵列电光、热光开关调制效率低、易失性以及开关单元选择存在局限性的弊端，本项目提出利用硫系相变材料的非易失性、高光学反差等特性，结合硅基桥形波导耦合结构，获得非微扰式的硅基非易失性光开关单元，通过拓扑组合实现光开关阵列的方案。围绕硅基混合波导非微扰光调控机制、2×2光开关工作机制两个关键科学问题，通过对高光学品质硫系相变材料、硅基混合波导光学性质、桥形波导光开关单元以及8×8光开关阵列芯片进行研究，旨在阐明硅基-硫系相变材料混合波导非微扰光调控机制，解决获得高性能2×2光开关单元的关键技术，最终实现低插损(~6dB)、低串扰(<-25dB)的宽带(~30nm)硅基8×8非易失性集成光开关阵列芯片，为光开关阵列在片上光互连、可编程光子学等研究领域的应用奠定坚实的科学基础。

本项目将相变材料与硅微环谐振器结合，验证了硅基-相变材料混合波导的光学性质可以在晶态和非晶态之间来回开关，得到波导的损耗调制和相位调制幅度分别为7.33 dB/μm和0.70 nm/μm。随后利用非对称方向耦合器的结构设计，将相变材料置于硅波导表面，获得了非易失性的1×2和2×2的光开关，且具有低插入损失(∼1dB)和一个紧凑的器件长度(∼30μm)，同时保持在30nm内较小的开关串扰（-10dB）。最后，利用在硅波导上掺杂形成的 PIN结加热器，成功实现了GST在硅光子集成上的高度可扩展电致相变，器件具有极低的插入损耗和驱动电压（1–2.5V），由于非易失性而调制能效高，并与CMOS工艺高度兼容。首次在光子集成回路上展示了1000多次的可逆电致相变。