Modulational instability of nonlinear polarization mode coupling in microresonators

We investigate frequency comb generation in the presence of polarization effects induced by nonlinear mode
coupling in microresonator devices. A set of coupled temporal Lugiato–Lefever equations are derived to model
the propagation dynamics, and an in-depth study is made of the modulational instability of their multistable
homogeneous steady-state solutions. It is shown that new kinds of instabilities can occur for co-propagating fields
that interact through nonlinear cross-phase modulation. These instabilities display properties that differ from
their scalar counterpart, and are shown to result in the generation of new types of incoherently coupled frequency
comb states.