Ultrahigh‐Order Harmonic Mode‐Locked Optoelectronic Oscillator

作者：Zhuoran Wang, Santiago Bernal, David V. Plant, Lawrence R. Chen · 发表于：Laser & Photonics Review · 年份：2026 · DOI：10.1002/lpor.202502273 · 研究领域：Advanced Fiber Laser Technologies、Advanced Photonic Communication Systems、Advanced Frequency and Time Standards

ABSTRACT Microwave frequency combs (MFCs) have attracted significant attention for applications in communication and detection. Mode‐locked optoelectronic oscillators (ML‐OEOs) have recently emerged as a powerful solution for generating high‐quality MFCs, leveraging the low loss of optical fibers. However, the performance of ML‐OEOs is often limited in terms of comb bandwidth and line spacing, mainly due to sidemode noise that restricts the achievable harmonic mode‐locking order. In this work, we demonstrate ultrahigh‐harmonic‐order mode‐locking in an amplified spontaneous emission (ASE)‐based OEO by incorporating a long zero‐dispersion recirculating loop (ZD‐RL) for sidemode suppression and a short RL to match the locking frequency. Using a 200‐m ZD‐RL together with a 4.6‐m short RL, we demonstrate 458th‐order harmonic mode‐locking with 50 dB sidemode suppression ratio (SMSR), generating 16 comb lines within a 10‐dB bandwidth of 657 MHz. By further shortening the RL to 2.2 m, the harmonic order is increased to 956, setting a new record for ML‐OEOs. The resulting comb features 91.5 MHz spacing, 53 dB SMSR, and 10 comb lines within a 10‐dB bandwidth of 824 MHz. Our results break through previous limitations on harmonic order in ML‐OEOs, providing a scalable route to large‐spacing, wideband microwave frequency combs for advanced communications and sensing.