CMOS兼容单谐振腔可见-红外光频梳产生机理与技术研究

Kerr optical frequency comb generated in microcavities can enable human to achieve ultraprecise optical frequency measurements, playing important roles in absolute frequency metrology and ultra-sophisticated detections in fundamental physics. Also it can be integrated with other chip-scale photonic devices, thus following the development trend of modern optics towards miniaturization and high-integration. Unfortunately, due to the strong material dispersion as well as high Rayleigh scattering at visible wavelengths that dramatically increases the intracavity loss, it is rather difficult to achieve the visible comb generation in micro-cavities.. In this proposal, microring cavities with ultrahigh Q-factor and super-low loss will be fabricated on the CMOS-compatible SiN photonic-integrated platform. The second- and third-order nonlinear parametric oscillations will be utilized to realize the generation of ultra-broadband frequency comb in a single micro-resonator, simultaneously covering the visible green, red, and infrared even mid-infrared wavelength range. Compared to traditional f-2f self-referencing approach, the proposed novel design of the 2f-3f self-referencing system can further reduce the complexity and improve the stability of the frequency-stabilizing and phase-locking system. We will also vigorously explore the effective realization methods of integratable, ultra-high repetition-rate, ultrashort-pulse laser sources. This research could promote technique developments and practical applications of micro-cavity frequency combs, as well as provide innovative ideas and key technical supports for the future development of very-large-scale photonic integrated circuits.

微腔克尔光频梳既使人类能够对光学频率实现极其精密测量、从而在频标计量及基础物理问题超高精度检测等方面发挥巨大作用，又能与其他光子器件实现片上集成、符合现代光学技术小型化与高集成化发展趋势。由于可见光波段的更强Rayleigh散射导致腔内损耗急剧增加且材料色散极强，因此微腔内可见光频梳产生尤为困难。本项目拟利用CMOS兼容的SiN光子集成平台，研制出具有超高Q值、超低损耗的微环谐振腔芯片；并利用新颖的二阶及三阶非线性参量振荡过程，实现在单个谐振腔内可同时输出覆盖可见绿光、红光、近红外乃至中红外波段的超宽带光频梳。本项目还将创新性地利用2f-3f自参考系统实现稳频、锁相，降低传统f-2f系统复杂程度并提高其稳定性与可靠性，并探索可片上集成的超高重频、超短脉冲激光源的有效实现途径。本项目能够积极促进微腔光频梳的技术发展与现实应用，并有望为超大规模光子集成回路的未来发展提供创新思想及关键技术支撑。

微腔光频梳由于其小型化以及超高重复频率的特点，有望在集成微波光子源、光通信、小型化光钟等领域产生前沿应用，具有重要的学术意义和应用价值。本项目开展了CMOS兼容单谐振腔可见-红外光频梳产生理论和实验研究，主要成果包括：建立并发展了描述微腔中非线性参量过程及Kerr光梳产生的理论模型，研究了多光子吸收和自由载流子效应以及高阶色散等对微腔光频梳时域和频域特性的影响；自主研制了CMOS兼容、Q值＞1.5×10^6的低损耗色散平坦微腔，并利用双腔激光模式选择机制实现了超高重频可调片上光频梳；研究了基于微腔的三次谐波产生技术，突破了基于CMOS兼容高折射率差波导微腔的红外-可见光梳产生难题并进行了实验验证，其最短波长覆盖了绿光516nm波段；提出了基于热调谐方法实现稳态单孤子光频梳及孤子晶体确定性产生的新技术，并分析了拉曼自频移效应对其稳定性和物理特性的影响；提出了温控微腔的耗散Kerr孤子产生新方法，实现了宽带耗散孤子产生；研究了不同注入光偏振下的宽带微腔光频梳产生以及自锁定正交偏振双光梳产生技术，探索了基于铌酸锂微腔的超4/5倍频程宽带红外光梳、基于交叉相位调制效应的正交偏振双光梳以及基于泵浦相位调制的微腔孤子光频梳产生技术；通过基于硅基波导中四波混频效应的时间透镜技术理论研究，提出了超快光信号测量新方法，能够为超高重频光频梳时频域特性测量与分析提供有效解决方案。在此基础之上，基于自主开发的低噪声微腔孤子光频梳，构建了高性能激光测距系统，为其实际应用提供了参考。此外，开展了片上模式转化器、集成光学滤波、片上相位与振幅调控等光子功能器件拓展性研究，可有助于促进光子芯片器件集成度和关键性能的提升。本项目研究成果为微腔光频梳应用于微波光子和分子光谱学等领域以及相关科学前沿高技术与交叉学科的创新发展提供了关键理论和技术基础。