近日，瑞士洛桑联邦理工学院Kippenberg, Tobias J.团队研究了无铜光子集成电路中的确定性孤子微梳。相关论文于2025年10月22日发表在《自然》杂志上。

基于微谐振器的芯片级光学频率梳（微梳）能够实现GHz到THz重复频率、宽带宽、紧凑外形因子和与晶圆级制造兼容的光频梳。Si₃N₄光子集成电路作为一个领先的平台，迄今已用于几乎所有系统级演示，从光通信、并行激光雷达、光频率合成、低噪声微波产生到并行卷积处理。

然而，由于确定性孤子微梳的生成具有很强的热不稳定性，该技术向实验室外实际应用的转化进展缓慢。虽然人们已经开发了各种各样的技术来激发孤子产生，包括脉冲泵浦、快速扫描和辅助激光泵浦，但这些技术并不能消除热效应，而且往往会通过增加额外的复杂性或减少可获得的孤子存在范围而损害微梳性能。

研究组克服了热效应并证明了Si₃N₄光子集成电路中确定性孤子的生成。他们在波导中追踪到意想不到的铜杂质热效应，这些杂质来自CMOS级硅晶片中的残留污染物，并在制造过程中进入Si₃N₄。通过开发除铜技术，他们大大降低了铜浓度，从而抑制了热效应。研究组证明了任意激光扫描轮廓和慢速激光扫描下耗散克尔孤子的确定性生成。该技术可直接应用于代工厂Si₃N₄器件的前端线工艺，为孤子微梳技术的实际应用扫除了关键障碍。

附：英文原文

Title: Deterministic soliton microcombs in Cu-free photonic integrated circuits

Author: Ji, Xinru, Li, Xurong, Qiu, Zheru, Wang, Rui Ning, Divall, Marta, Gelash, Andrey, Lihachev, Grigory, Kippenberg, Tobias J.

Issue&Volume: 2025-10-22

Abstract: Chip-scale optical frequency combs based on microresonators (microcombs) have provided access to optical combs with GHz-to-THz repetition rates, broad bandwidth, compact form factors and compatibility with wafer-scale manufacturing1. Si3N4 photonic integrated circuits emerged as a leading platform and have been used in nearly all system-level demonstrations so far, ranging from optical communications2, parallel lidar3, optical frequency synthesis4, low-noise microwave generation5 to parallel convolutional processing6. Yet, transitioning to real-world deployment outside laboratories has been compounded by the difficulty of deterministic soliton microcomb generation, primarily due to strong thermal instabilities. Although a variety of techniques have been developed to initiate soliton generation, including pulsed pumping, fast scanning and auxiliary-laser pumping7,8,9,10,11, these techniques do not eliminate thermal effects and often compromise microcomb performance, either by adding additional complexity or by reducing the accessible soliton existence range. Here we overcome thermal effects and demonstrate deterministic soliton generation in Si3N4 photonic integrated circuits. We trace thermal effects to unexpected copper impurities within the waveguides, which originate from residual contaminants in CMOS-grade Si wafers and are gettered into Si3N4 during fabrication. By developing copper removal techniques, we substantially reduce copper concentration and thereby mitigate thermal effects. We demonstrate successful dissipative Kerr soliton generation with arbitrary laser scanning profiles and slow laser scanning. Our techniques can be readily applied to front-end-of-line processing of Si3N4 devices in foundries, removing a key obstacle to the deployment of soliton microcomb technology.

DOI: 10.1038/s41586-025-09598-4

Source: https://www.nature.com/articles/s41586-025-09598-4