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).

Ultra-Precise Microwaves from a Microchip: New Integrated Photonics Breakthrough Paves the Way for Compact, Low-Noise Signal Generation

Imagine transferring massive amounts of data or powering next-gen radar systems—all from a device no larger than a microchip. A new study published in the IEEE Journal of Selected Topics in Quantum Electronics details a major leap in microwave signal generation using integrated photonics.

By leveraging a silicon-based “microcomb” and a technique called two-point optical frequency division (2P-OFD), researchers have demonstrated a chip-scale system that generates ultra-stable, low-noise microwave signals—without the bulk and power demands of traditional equipment. The key lies in locking two diode lasers to an optical reference cavity and dividing their frequency difference via the harmonics of the microcomb.

This breakthrough opens the door to compact, energy-efficient technologies for 6G networks, precision timing, satellite communications, and more. The system’s compatibility with standard diode lasers and its resistance to environmental noise make it a strong candidate for real-world applications across both civilian and defense sectors.

Original Paper:
Coherent optical-to-microwave link using an integrated microcomb
IEEE Journal of Selected Topics in Quantum Electronics
DOI: 10.1109/JSTQE.2024.3451301  

Image Caption: Photonic chip-based low-noise microwave generation using the optical frequency division technique.