近日，美国国家标准与技术研究院的Scott A. Diddams&Igor Kudelin及其研究团队取得一项新进展。经过不懈努力，他们研制出基于光子芯片的低噪声微波振荡器。相关研究成果已于2024年3月6日在国际权威学术期刊《自然》上发表。

据悉，许多现代技术都依赖于微波信号的低相位噪声和精确的时序稳定性。微波光子学领域已经取得了重大进展，通常利用频率梳对超稳定光基准进行下变频，产生低噪声微波信号。然而，这样的系统是由大块或光纤构成的，很难进一步减小尺寸和功耗。

在这项工作中，研究人员通过利用集成光子学的进展来展示通过两点光学分频产生低噪声微波来解决这一挑战。将窄线宽自注入锁定集成激光器稳定在一个微型Fabry–Pérot腔中，并用一个高效的暗孤子频率梳来划分激光器之间的频率间隙。微梳的稳定输出光检测产生20GHz的微波信号，在100Hz偏移频率下相位噪声为96dBcHz^-1，在10kHz偏移频率下相位噪声降至-135dBcHz^-1，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异构地集成在一个芯片上，为光子学在高精度导航、通信和授时系统中的应用提供了重大突破。

附：英文原文

Title: Photonic chip-based low-noise microwave oscillator

Author: Kudelin, Igor, Groman, William, Ji, Qing-Xin, Guo, Joel, Kelleher, Megan L., Lee, Dahyeon, Nakamura, Takuma, McLemore, Charles A., Shirmohammadi, Pedram, Hanifi, Samin, Cheng, Haotian, Jin, Naijun, Wu, Lue, Halladay, Samuel, Luo, Yizhi, Dai, Zhaowei, Jin, Warren, Bai, Junwu, Liu, Yifan, Zhang, Wei, Xiang, Chao, Chang, Lin, Iltchenko, Vladimir, Miller, Owen, Matsko, Andrey, Bowers, Steven M., Rakich, Peter T., Campbell, Joe C., Bowers, John E., Vahala, Kerry J., Quinlan, Franklyn, Diddams, Scott A.

Issue&Volume: 2024-03-06

Abstract: 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 20GHz with phase noise of 96dBcHz^-1 at 100Hz offset frequency that decreases to -135dBcHz^-1 at 10kHz 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.

DOI: 10.1038/s41586-024-07058-z

Source: https://www.nature.com/articles/s41586-024-07058-z