National Institute of Standards and Technology, Boulder, CO, USA.
Department of Physics, University of Colorado Boulder, Boulder, CO, USA.
Nature. 2024 Mar;627(8004):534-539. doi: 10.1038/s41586-024-07058-z. Epub 2024 Mar 6.
Numerous modern technologies are reliant on the low-phase noise and exquisite timing stability of microwave signals. Substantial progress has been made in the field of microwave photonics, whereby low-noise microwave signals are generated by the down-conversion of ultrastable optical references using a frequency comb. Such systems, however, are constructed with bulk or fibre optics and are difficult to further reduce in size and power consumption. In this work we address this challenge by leveraging advances in integrated photonics to demonstrate low-noise microwave generation via two-point optical frequency division. Narrow-linewidth self-injection-locked integrated lasers are stabilized to a miniature Fabry-Pérot cavity, and the frequency gap between the lasers is divided with an efficient dark soliton frequency comb. The stabilized output of the microcomb is photodetected to produce a microwave signal at 20 GHz with phase noise of -96 dBc Hz at 100 Hz offset frequency that decreases to -135 dBc Hz at 10 kHz offset-values that are unprecedented for an integrated photonic system. All photonic components can be heterogeneously integrated on a single chip, providing a significant advance for the application of photonics to high-precision navigation, communication and timing systems.
许多现代技术都依赖于微波信号的低相位噪声和精密的时频稳定度。在微波光子学领域已经取得了重大进展，通过使用频梳将超稳光参考源下变频，可以产生低噪声微波信号。然而，这些系统是基于体光学或光纤构建的，很难进一步减小尺寸和功耗。在这项工作中，我们利用集成光子学的进展来应对这一挑战，通过两点光频分演示了低噪声微波产生。窄线宽自注入锁定集成激光器被稳定到微型法布里-珀罗腔上，通过高效暗孤子频梳来分割激光器之间的频率间隔。微梳的稳定输出通过光电探测器产生 20GHz 的微波信号，在 100Hz 偏移频率下的相位噪声为-96dBc/Hz，在 10kHz 偏移下降至-135dBc/Hz，这对于集成光子系统来说是前所未有的。所有的光子元件都可以在单个芯片上异质集成，为光子学在高精度导航、通信和定时系统中的应用提供了重要的进展。
