Integrated optical frequency comb technologies

Optical frequency combs offer an unrivalled degree of frequency measurement precision that underpins the advance of modern technology in both fundamental science and commercial contexts. Recent progress in integrated photonics provides an attractive route to realize optical frequency comb sources in a compact, low-cost and energy-efficient manner by leveraging tightly-confined waveguide platforms and wafer-scale mass-manufacturing in photonic foundries, potentially revolutionizing the fields of information processing, time–frequency metrology and sensing. In this Review Article, we comprehensively examine the strategies for optical frequency comb generation in integrated photonics and provide detailed appraisals of those strategies in the context of prospective applications. The progress of high-level integration of optical frequency combs in photonic integrated circuits is summarized and a roadmap is proposed for transferring advanced optical frequency comb systems from the laboratory to the wider world.