Coupled-mode theory of the polarization dynamics inside a microring resonator with a uniaxial core

The use of a uniaxial birefringent material such as lithium niobate (LiNbO3, LN) as the core of a microring resonator leads to coupling between transverse-electric and transverse-magnetic modes. We develop a theoretical framework to study polarization evolution inside such a resonator. We write Maxwell's equations in the form of a Schrodinger equation and use it to obtain coupled-mode equations modeling the continuous reorientation of the optic axis as light propagates inside the microring resonator. We show that the mode-coupling problem is isomorphic to a quantum-mechanical two-level system modulated in frequency and driven by a classical optical field. We analyze the polarization coupling by using the well-known techniques of quantum mechanics such as time-dependent perturbation theory, the rotating-wave approximation, and the adiabatic approximation. As an example, we consider a LN ring resonator and describe the evolution of the state of polarization of injected light along the ring's circumference.

Automated summary

The article investigates the polarization evolution problem when using lithium niobate as the core of a microring resonator, analyzing the polarization coupling using quantum mechanics techniques. It specifically describes the evolution of the polarization state of injected light along the circular path in a lithium niobate ring resonator.