Frequency combs generated from rotational Doppler effect

In frequency domain, power spectrum density with evenly spaced discrete lines forms a frequency comb, which has become a fundamental physical concept for wave. Especially, in optical electromagnetic wavebands, an optical frequency comb plays a crucial role for a variety of precision measurement technologies and has become one of the representative breakthroughs in modern physics. To extend the study of frequency comb to other wave region would be an interesting and important task. One significant challenge is to develop a general method suitable to different waves. Here, by manipulation one of the essence natures of wave, orbital angular momentum (OAM), we demonstrate an general approach to produce a frequency comb based on a rotational Doppler effect with the OAM comb. We experimentally generate and verify frequency comb with teeth up to 10. Our results not only provide a general way for the frequency comb generation suitable to various waves but also may open up possibilities for application of frequency comb in more types of wave.