Researchers from Tsinghua University and KAIST have demonstrated an innovative approach to synthesizing ultralow-noise microwaves using a chip-scale silica wedge microresonator. Their study, published in the IEEE Journal of Selected Topics in Quantum Electronics, leverages a phenomenon known as the “quiet point” to reduce phase noise beyond the capabilities of leading electronic oscillators.
Using soliton microcombs and a technique called injection locking, the team achieved a single-sideband phase noise as low as –143 dBc/Hz at a 100 kHz offset for a 10 GHz signal—surpassing some of the most advanced commercial microwave sources. This improvement is crucial for applications such as radar, 6G wireless communication, and high-speed signal processing, where low phase noise and long-term frequency stability are essential.
The findings highlight the growing potential of integrated photonics and optical frequency division for next-generation microwave synthesis on a compact, power-efficient chip. This approach balances short-term jitter suppression through soliton dynamics and long-term drift reduction via injection locking—offering a powerful, scalable solution for high-precision technologies.
Original Paper:
Injection locked low noise chip-based silica soliton microwave oscillator
IEEE Journal of Selected Topics in Quantum Electronics
DOI: 10.1109/JSTQE.2024.3423774
Image Caption: Illustration of a silica wedge microresonator soliton-based low noise microwave generator. Phase modulation of the pump laser leads to injection locking that suppresses long-term drift (blue curve), while soliton dynamics purify short-term noise (green curve), resulting in a stable low-noise microwave output (yellow curve).
