Kerr frequency comb generation relies on dedicated waveguide platforms that are optimized toward ultralow loss while offering comparatively limited functionality restricted to passive building blocks. In contrast to that, the silicon-photonic platform offers a highly developed portfolio of high-performance devices, but suffers from strong two-photon absorption (TPA) and subsequent free-carrier absorption (FCA) at near-infrared telecommunication wavelengths, thereby rendering Kerr comb generation a challenge. Here we present a model to investigate the impact of TPA and FCA on Kerr comb formation. Our model combines a modified version of the Lugiato-Lefever equation with a refined relation to precisely describe the fast space and time dependence of the free-carrier concentration along the circumference of the microresonator. Using this refined model, we derive conditions for modulation instability, in particular for necessary pump powers depending on TPA parameters and free-carrier lifetimes. We validate our analytical predictions by time integration and study the impact of fast free-carrier dynamics on Kerr comb formation. We find that silicon microresonators may be suitable for Kerr comb generation in the NIR, provided that the dwell time of the TPA-generated free carriers in the waveguide core is reduced by a reverse-biased $p\text{−}i\text{−}n$-junction and that the pump parameters are chosen appropriately.

中文翻译：

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双光子吸收和快速自由载流子动力学影响下硅微谐振器中克尔梳的产生分析

克尔频率梳生成依赖于专门的波导平台，这些平台针对超低损耗进行了优化，同时提供受限于无源构建块的相对有限的功能。与此相反，硅光子平台提供了高度发达的高性能设备组合，但在近红外通信波长处存在强双光子吸收 (TPA) 和随后的自由载流子吸收 (FCA)，从而导致克尔梳代是一个挑战。在这里，我们提出了一个模型来研究 TPA 和 FCA 对克尔梳形成的影响。我们的模型将 Lugiato-Lefever 方程的修改版本与改进的关系相结合，以精确描述沿微谐振器圆周的自由载流子浓度的快速空间和时间依赖性。使用这个精致的模型，我们推导出调制不稳定性的条件，特别是根据 TPA 参数和自由载流子寿命所需的泵浦功率。我们通过时间积分验证了我们的分析预测，并研究了快速自由载流子动力学对克尔梳形成的影响。我们发现硅微谐振器可能适用于 NIR 中的克尔梳生成，前提是 TPA 生成的自由载流子在波导芯中的驻留时间通过反向偏置减少$磷\text{-}\mathrm{一世}\text{-}n$-junction 并且泵参数选择适当。