Laser technology: The Turbulence and the Comb

While the light of an ordinary laser only has one single, well-defined wavelength, a so-called “frequency comb” consists of different light frequencies, which are precisely arranged at regular distances, much like the teeth of a comb. Such frequency combs are difficult to generate. Now, researchers have succeeded in producing frequency combs using simple circular quantum cascade lasers – a result that seemed to contradict conventional laser theories completely.