The Editorial

Thousands of scientific contributions devoted to optical frequency combs were published during the last decade, covering groundbreaking advancements in generation of multiple equidistant coherent optical harmonics and their applications in science and technology. The interest in these devices was fueled by their scalability and potential to convert a lab-scale experiment to an opto-electronic chip. Usefulness of on-chip optical frequency combs was proven in the generation of pure optical and microwave signals and waveforms as well as optical and microwave metrology. Comb technology also impacted quantum science and quantum technology and contributed to the studies and development of new optical material platforms. They are indispensable in modern fundamental nonlinear optics as a rich source of multidimensional optical phenomena. Usefulness of microcombs in timekeeping, telecommunications, exoplanet detection, ranging, AI, and medicine has also been noticed.