Electro‐Optic Frequency Combs: Theory, Characteristics, and Applications

Abstract Optical frequency combs (OFCs) are a unique kind of light source, which are represented as a series of equally spaced coherent spectral lines in the frequency domain. OFCs can mainly be divided into mode‐locked lasers, Kerr frequency combs, and electro‐optic frequency combs (E‐O combs), which have broad applications in optical communications, frequency metrology, atomic clocks, distance ranging, spectroscopy, and arbitrary waveform generation. Among them, E‐O combs feature some unique advantages, such as fast tunable repetition rate, high sidebands power, and reconfigurability of the comb spectrum. Especially in recent years, with the development of micro–nano processing technology, on‐chip E‐O combs have become a dynamic research topic with many fundamental scientific problems as well as engineering applications for further exploration. To summarize the past development and envision the prosperous future of E‐O combs, the area of E‐O combs is reviewed from the following aspects: development of E‐O combs; theory including the generation process of E‐O combs and the electro‐optic modulation models; important techniques including flattening, broadening, noise, and stability controlling; applications including communications, ranging, spectroscopy, wavelength calibration of astronomical spectrographs, and microwave generation; and pros and cons when compared with other OFCs.