Nonlinear mode coupling in whispering-gallery-mode resonators
  We present a first principle derivation of the coupled nonlinear Schr\"{o}dinger equations that govern the interaction between two families of modes with different transverse profiles in a generic whispering-gallery-mode resonator. We find regions of modulational instability and the existence of trains of bright solitons both in the normal and in the anomalous dispersion regime. 
Giuseppe D'Aguanno and Curtis R. Menyuk
physics.optics