近日，美国哥伦比亚大学的Alexander L.Gaeta及其研究团队取得一项新进展。经过不懈努力，他们使用单激光器实现片上全光学分频。相关研究成果已于2024年3月11日在国际权威学术期刊《自然》上发表。

该研究团队成功展示了在光子芯片上实现的全光学OFD技术。他们通过单一连续波激光泵浦，同步了两个不同动态状态的克尔微谐振器。研究人员将光参量振荡器signal场和idler场之间太赫兹拍频的固有稳定性，转移到了克尔孤子梳的微波频率上，并通过耦合波导实现同步，全程无需电子锁定。

实验结果显示，227GHz和16GHz孤子梳的OFD因子分别高达N = 34和468。尤为值得一提的是，利用OFD技术，16GHz孤子梳的相位噪声降低了46dB，从而在集成光子平台中实现了微波噪声的最低水平。这一研究成果不仅提供了一种简单而高效的OFD执行方法，还为芯片级器件的研发开辟了新的途径。这种器件能够产生与计量实验室中生成的最纯净声调相媲美的微波频率。

据悉，频谱纯净的微波信号的产生是基础科学和应用科学的关键功能，包括计量和通信。光学频率梳使强大的光学分频技术(OFD)能够产生最高质量的微波振荡。然而，现有的OFD实现方式需要多个激光器，涉及光学稳定性和电子反馈组件，导致器件占地面积不兼容集成到紧凑且鲁棒的光子平台中。

附：英文原文

Title: All-optical frequency division on-chip using a single laser

Author: Zhao, Yun, Jang, Jae K., Beals, Garrett J., McNulty, Karl J., Ji, Xingchen, Okawachi, Yoshitomo, Lipson, Michal, Gaeta, Alexander L.

Issue&Volume: 2024-03-11

Abstract: The generation of spectrally pure microwave signals is a critical functionality in fundamental and applied sciences, including metrology and communications. Optical frequency combs enable the powerful technique of optical frequency division (OFD) to produce microwave oscillations of the highest quality. Current implementations of OFD require multiple lasers, with space- and energy-consuming optical stabilization and electronic feedback components, resulting in device footprints incompatible with integration into a compact and robust photonic platform. Here we demonstrate all-optical OFD on a photonic chip by synchronizing two distinct dynamical states of Kerr microresonators pumped by a single continuous-wave laser. The inherent stability of the terahertz beat frequency between the signal and idler fields of an optical parametric oscillator is transferred to a microwave frequency of a Kerr soliton comb, and synchronization is achieved via a coupling waveguide without the need for electronic locking. OFD factors of N = 34 and 468 are achieved for 227GHz and 16GHz soliton combs, respectively. In particular, OFD enables a 46dB phase-noise reduction for the 16GHz soliton comb, resulting in the lowest microwave noise observed in an integrated photonics platform. Our work represents a simple, effective approach for performing OFD and provides a pathway towards chip-scale devices that can generate microwave frequencies comparable to the purest tones produced in metrological laboratories.

DOI: 10.1038/s41586-024-07136-2

Source: https://www.nature.com/articles/s41586-024-07136-2