Kerr frequency combs of axial-azimuthal modes in SNAP fiber resonator

Here we develop a model of nonlinear dynamics of axial-azimuthal whispering gallery modes (WGMs) propagating at the boundary of a cylindrical microresonator with small variations of the effective radius. The model comprises a system of coupled nonlinear equations for different azimuthal modes, each experiencing evolution along the axial direction. Using the model, we optimize the parameters of the pump and obtain the generation of an axial-azimuthal optical frequency comb with a repetition rate of 12 GHz.