Abstract. The exploration of physical degrees of freedom of light with infinite dimensionality, such as orbital angular momentum (OAM) and frequency, has profoundly reshaped the landscape of modern optics, with representative photonic functional devices including optical vortex emitters and frequency combs. In nanophotonics, whispering gallery mode microresonators naturally support applications based on the OAM of light and have been employed as on-chip emitters of monochromatic optical vo...