Universal formation dynamics and noise of Kerr-frequency combs in microresonators

Optical frequency combs allow for precise measurement of optical frequencies and are used in a growing number of applications beyond spectroscopy and optical frequency metrology. A class of compact microresonator based frequency comb generators has emerged recently based on (hyper)-parametric frequency conversion, mediated by the Kerr-non-linearity, of a continuous wave laser beam. Despite the rapid progress and the emergence of a wide variety of micro-resonator Kerr-comb platforms, an understanding of the dynamics of the Kerr comb formation is still lacking. In particular the question in which regime low phase noise performance can be achieved has so far not been answered but is of critical importance for future application of this technology. Here an universal, platform independent understanding of the Kerr-comb formation dynamics based on experimental observations in crystalline MgF2 and planar Si3N4 comb generators is given. This explains a wide range of hereto not understood phenomena and reveals for the first time the underlying condition for low phase noise performance.