用于波分复用光互连的片上多波长光源产生机理与实现方法研究

Optical multiplexing techniques are demanded to meet the tremendous bandwidth requirements of on-chip interconnects and leverage the inherent huge bandwidth of optical communications. Among various schemes, wavelength-division multiplexing is the most promising one to satisfy the demands in bandwidth, integration density and power consumption. On-chip, wavelength-spacing stabilized, wavelength-number scalable and low-power consumption multi-wavelength light source is the remaining bottleneck of on-chip WDM interconnects. On-chip integrated comb source could overcome the shortcomings in power consumption, wavelength stability, scalability of current light sources based on DFB laser arrays, and provide a stable multi-wavelength output from a single source. To further break out from the limitations in requiring off-chip pump source, poor output spectral flatness and lack of control on the noise characteristics, this project proposes a novel method based on a multiplexed cavity with a feedback loop, in order to control the parametric gain profile in the nonlinear cavity, reduce the pump power requirements and improve the spectral flatness, power conversion efficiency and spectral coherence. By combining the linewidth control of lasers and low-noise power amplification techniques, realizing a low-noise and narrow linewidth pump source and its efficient coupling with silicon devices will be explored. This would build solid foundation for solving the problems in key mechanism and methodology in realizing on-chip pumped, microcavity multi-wavelength light sources, and for the development of on-chip WDM interconnect technologies.

用于片上光互连的复用技术是发挥光通信带宽优势、满足片上超高速率互连带宽需求的必由途径。在各种复用技术中，波分复用最有望满足片内带宽、集成密度、功耗的要求。可片上集成、波长间距稳定、波长数量可扩展、低功耗的多波长光源器件是片上波分复用光互连尚未被攻克的技术瓶颈。基于光频梳的片上光源能提供波长间距精准、线宽窄的多波长输出，克服现有分立激光阵列的功耗大、波长控制复杂、可扩展性差的缺陷。为了突破现有非线性微腔光梳器件需要片外泵浦源、输出谱线平坦度差、噪声特性难以调控的局限，本项目提出了基于辅助反馈腔的复合微腔光梳的创新思路，调控非线性微腔中的参量增益动力学过程，降低泵浦功率要求，提高谱线平坦度与有效功率转换效率，抑制光谱噪声；融合激光线宽控制与低噪声功率放大方法，获得窄线宽、低噪声泵浦源，并与硅基器件高效耦合。解决片上泵浦的微腔多波长光源的核心机理和关键方法，为片上互连波分复用技术的发展奠定基础。

为满足片上超高带宽互连的需求，片上波分复用光互联具有重要的研究价值，其中可片上集成、波长间距稳定、波长数可扩展的多波长光源对于片上光互连技术的发展具有重要的意义。但现有分立激光阵列功耗大、波长控制复杂、可扩展性差，成为了制约片上高速波分复用光互联技术发展的一个瓶颈。非线性微腔光梳技术具有实现片上波分复用光互联光源的潜力，但需要解决其实现中的关键理论和工艺问题，克服泵浦阈值高、谱线不平坦等不足。本项目从解决未来片上多波长光源技术的核心科学与技术问题的角度出发，提出探索波长间距精准的基于片上光频梳光源以克服上述缺陷。本项目从硅基微腔光梳理论建模及仿真、片上非线性波导微腔及有源器件设计、非线性微腔及硅基兼容有源器件制备方法、片上微腔表征与光通信验证等方面开展了系统研究工作。在建立复合腔非线性动力学模型的基础上提出了一种泵浦光反馈的低阈值微腔光梳生成方法，分别提出了低色散和无热化非线性氮化硅波导设计；建立了硅基非线性微腔器件和mW级Si基键合激光器和半导体光放大器的制备工艺，制备出了Q值达到80万的低损耗、低色散氮化硅微腔；发现了高Q值微腔器件中对向传输光之间非线性克尔效应导致的自发对称性破缺现象，实现了梳齿间隔100GHz的时域耗散克尔孤子光频梳的产生；突破了基于锁模脉冲光源的双光梳产生方法与关键技术，提出了相应的双光梳高精度光谱测量方法并搭建了高Q微腔的光谱幅相的动态高分辨率特性表征平台；在信道间隔100GHz的8个波长上演示验证了硅基微腔光频梳输出作为种子光源的每波长25Gb/s的无误码光通信传输的可行性。在国内外重要刊物和国际重要学术会议上发表论文81篇(其中SCI32篇，国际会议特邀报告4篇），授权国际和国家发明专利12 项（其中美国专利授权4项），培养博士、硕士18 人，博士后1人。有关成果可为片上互连技术的发展提供技术积累，也可应用于其他光谱测量、微波光子等领域。