基于亚波长光栅的硅基片上模式复用器

On-chip mode-division multiplexing(MDM) offers a new dimension to increase the capacity of silicon-on-insulator (SOI) optical links. The key to realize on-chip MDM is an efficient mode (de)multiplexer. Currently, an efficient mode multiplexer built on the SOI platform with low insertion loss, low crosstalk, and large fabrication tolerance attracts much attention. The main purpose of this project is to study physical mechanism of the interactions between silicon sub-wavelength grating waveguide and multimode waveguide, which could provide a new method to realize an on-chip efficient mode (de)multiplexer. The study results may indicate several new breakthroughs on the theories and technologies about mode (de)multiplexers. To achieve these, following major studies will be carried out: the design and fabrication of silicon sub-wavelength grating waveguide with low transmission loss; adiabatic transformer section between the conventional nanowire waveguide and sub-wavelength grating waveguide; the mechanism of selective mode coupling between the sub-wavelength grating waveguide and silicon multimode waveguide. The structures of sub-wavelength grating waveguides are designed carefully to enhance the selective mode coupling and decrease the channel crosstalk. The proposed mode (de)multiplexer has the advantages of low crosstalk, high fabrication tolerance, and the capability of large scale integration, which will be an important component for the development of ultra-large capability optical network.

片上模分复用技术能大幅提升光通信系统的传输容量、降低系统体积成本，可服务于大数据和移动互联网的发展。目前片上集成模分复用技术及模式复用器吸引了研究人员的兴趣，如何实现低信道串扰与高制作容差，同时兼顾可扩展性的模式复用器是研究热点。本项目拟研究一种基于硅基亚波长光栅波导与多模波导的耦合复用机理的模式复用器。拟围绕亚波长光栅波导低损光传输、与硅纳米线波导绝热耦合、亚波长光栅波导与多模波导的模式选择性耦合等核心科学问题，开展集成复用器件的理论分析、芯片研制与系统测试工作。基于亚波长光栅的高调节自由度特性，针对不同模式信道分别优化亚波长光栅波导结构，增强模式耦合的选择性，降低信道串扰。利用亚波长光栅波导与多模波导的有效折射率变化斜率匹配，提高耦合对工艺的容忍度。本器件方案具有低信道串扰、高制作容差、可大规模扩展集成等优点，可望促进超大容量光通信系统的发展。

随着大数据和移动互联网的快速发展，光通信容量持续增长，片上模分复用技术能大幅提升光通信系统的传输容量、降低系统体积成本，因而其吸引了研究人员的广泛兴趣。如何实现低信道串扰与高制作容差，同时兼顾可扩展性的模式复用器是当前的研究热点。本项目围绕亚波长光栅波导低损光传输、与硅纳米线波导绝热耦合、亚波长光栅波导与多模波导的模式选择性耦合等核心科学问题，开展集成模式调控器件的理论分析、芯片研制与系统测试工作。基于亚波长光栅的高调节自由度特性，针对不同模式信道分别优化亚波长光栅波导结构，增强模式耦合的选择性，降低信道串扰。利用亚波长光栅波导与多模波导的有效折射率变化斜率匹配，提高耦合对工艺的容忍度。重要研究结果包括：建立硅基亚波长光栅波导仿真模型；建立亚波长光栅波导与硅多模波导的模式耦合仿真模型；研制基于亚波长光栅的硅基多通道模式复用器，通道数为11，插损低于2.6 dB，串扰低于-15.4 dB，并开展了高速光信号测试，该器件具备通道数易于扩展的特点；研制基于倾斜亚波长光栅结构的硅基模式转换器，长度约为6微米，具有超紧凑的特点；研制基于亚波长光栅的偏振分束旋转器，具备高制作容差的特点，对波导宽度的容忍度高达50 nm；研制基于亚波长光栅结构的反向耦合的模式滤波器，用于滤除多模波导中任意模式而不影响其他模式的正常传输。基于亚波长光栅的硅基模式偏振调控器件方案具有低信道串扰、高制作容差、可大规模扩展集成等优点，可望促进超大容量光通信系统的发展。

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