Optical frequency combs, which emit pulses of light at discrete, equally spaced frequencies, are cornerstones of modern-day frequency metrology, precision spectroscopy, astronomical observations, ultrafast optics and quantum information1–7. Chip-scale frequency combs, based on the Kerr and Raman nonlinearities in monolithic microresonators with ultrahigh quality factors8–10, have recently led to progress in optical clockwork and observations of temporal cavity solitons11–14. But the chromatic dispersion within a laser cavity, which determines the comb formation15,16, is usually difficult to tune with an electric field, whether in microcavities or fibre cavities. Such electrically dynamic control could bridge optical frequency combs and optoelectronics, enabling diverse comb outputs in one resonator with fast and convenient tunability. Arising from its exceptional Fermi–Dirac tunability and ultrafast carrier mobility17–19, graphene has a complex optical dispersion determined by its optical conductivity, which can be tuned through a gate voltage20,21. This has brought about optoelectronic advances such as modulators22,23, photodetectors24 and controllable plasmonics25,26. Here we demonstrate the gated intracavity tunability of graphene-based optical frequency combs, by coupling the gate-tunable optical conductivity to a silicon nitride photonic microresonator, thus modulating its second- and higher-order chromatic dispersions by altering the Fermi level. Preserving cavity quality factors up to 106 in the graphene-based comb, we implement a dual-layer ion-gel-gated transistor to tune the Fermi level of graphene across the range 0.45–0.65 electronvolts, under single-volt-level control. We use this to produce charge-tunable primary comb lines from 2.3 terahertz to 7.2 terahertz, coherent Kerr frequency combs, controllable Cherenkov radiation and controllable soliton states, all in a single microcavity. We further demonstrate voltage-tunable transitions from periodic soliton crystals to crystals with defects, mapped by our ultrafast second-harmonic optical autocorrelation. This heterogeneous graphene microcavity, which combines single-atomic-layer nanoscience and ultrafast optoelectronics, will help to improve our understanding of dynamical frequency combs and ultrafast optics.Coupling graphene sheets with a silicon nitride ring microresonator allows the nonlinear cavity dynamics to be altered by a gate voltage, resulting in tunable, chip-scale, optical frequency combs.

中文翻译：

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石墨烯-氮化物微谐振器中的栅极可调频率梳

光频梳以离散的、等距的频率发射光脉冲，是现代频率计量学、精密光谱学、天文观测、超快光学和量子信息的基石1-7。芯片级频率梳基于具有超高品质因数的单片微谐振器中的克尔和拉曼非线性 8-10，最近在光学时钟和时间腔孤子观察方面取得了进展 11-14。但是决定梳状结构 15,16 的激光腔内的色散通常很难用电场调整，无论是在微腔还是光纤腔中。这种电动态控制可以桥接光频梳和光电子学，在一个谐振器中实现多种梳状输出，并具有快速方便的可调性。由于其卓越的费米-狄拉克可调性和超快载流子迁移率 17-19，石墨烯具有复杂的光学色散，由其光导率决定，可以通过栅极电压进行调整 20,21。这带来了光电方面的进步，例如调制器 22、23、光电探测器 24 和可控等离子体 25、26。在这里，我们通过将栅极可调光导率耦合到氮化硅光子微谐振器，从而通过改变费米能级来调制其二阶和更高阶色散，从而展示了基于石墨烯的光频率梳的门控腔内可调性。在基于石墨烯的梳子中保持高达 106 的腔品质因子，我们实施了双层离子凝胶门控晶体管，以在 0.45-0.65 电子伏特范围内调整石墨烯的费米能级，在单伏电平控制下。我们使用它在单个微腔中产生从 2.3 太赫兹到 7.2 太赫兹的电荷可调主梳线、相干克尔频率梳、可控切伦科夫辐射和可控孤子态。我们进一步证明了从周期性孤子晶体到具有缺陷的晶体的电压可调跃迁，由我们的超快二次谐波光学自相关映射。这种结合单原子层纳米科学和超快光电子学的异质石墨烯微腔将有助于提高我们对动态频率梳和超快光学的理解。将石墨烯片与氮化硅环形微谐振器耦合允许非线性腔动力学通过栅极电压，从而产生可调谐的芯片级光频梳。我们使用它在单个微腔中产生从 2.3 太赫兹到 7.2 太赫兹的电荷可调主梳线、相干克尔频率梳、可控切伦科夫辐射和可控孤子态。我们进一步证明了从周期性孤子晶体到具有缺陷的晶体的电压可调跃迁，由我们的超快二次谐波光学自相关映射。这种结合单原子层纳米科学和超快光电子学的异质石墨烯微腔将有助于提高我们对动态频率梳和超快光学的理解。将石墨烯片与氮化硅环形微谐振器耦合允许非线性腔动力学通过栅极电压，从而产生可调谐的芯片级光频梳。我们使用它在单个微腔中产生从 2.3 太赫兹到 7.2 太赫兹的电荷可调主梳线、相干克尔频率梳、可控切伦科夫辐射和可控孤子态。我们进一步证明了从周期性孤子晶体到具有缺陷的晶体的电压可调跃迁，由我们的超快二次谐波光学自相关映射。这种结合单原子层纳米科学和超快光电子学的异质石墨烯微腔将有助于提高我们对动态频率梳和超快光学的理解。将石墨烯片与氮化硅环形微谐振器耦合允许非线性腔动力学通过栅极电压，从而产生可调谐的芯片级光频梳。2 太赫兹、相干克尔频率梳、可控切伦科夫辐射和可控孤子态，全部位于单个微腔中。我们进一步证明了从周期性孤子晶体到具有缺陷的晶体的电压可调跃迁，由我们的超快二次谐波光学自相关映射。这种结合单原子层纳米科学和超快光电子学的异质石墨烯微腔将有助于提高我们对动态频率梳和超快光学的理解。将石墨烯片与氮化硅环形微谐振器耦合允许非线性腔动力学通过栅极电压，从而产生可调谐的芯片级光频梳。2 太赫兹、相干克尔频率梳、可控切伦科夫辐射和可控孤子态，全部位于单个微腔中。我们进一步证明了从周期性孤子晶体到具有缺陷的晶体的电压可调跃迁，由我们的超快二次谐波光学自相关映射。这种结合单原子层纳米科学和超快光电子学的异质石墨烯微腔将有助于提高我们对动态频率梳和超快光学的理解。将石墨烯片与氮化硅环形微谐振器耦合允许非线性腔动力学通过栅极电压，从而产生可调谐的芯片级光频梳。我们进一步证明了从周期性孤子晶体到具有缺陷的晶体的电压可调跃迁，由我们的超快二次谐波光学自相关映射。这种结合单原子层纳米科学和超快光电子学的异质石墨烯微腔将有助于提高我们对动态频率梳和超快光学的理解。将石墨烯片与氮化硅环形微谐振器耦合允许非线性腔动力学通过栅极电压，从而产生可调谐的芯片级光频梳。我们进一步证明了从周期性孤子晶体到具有缺陷的晶体的电压可调跃迁，由我们的超快二次谐波光学自相关映射。这种结合单原子层纳米科学和超快光电子学的异质石墨烯微腔将有助于提高我们对动态频率梳和超快光学的理解。将石墨烯片与氮化硅环形微谐振器耦合允许非线性腔动力学通过栅极电压，从而产生可调谐的芯片级光频梳。