<i>N</i>-order generalized-temporal coupled mode theory (g-TCMT) model: extending the spectral range for arbitrary coupling of optical resonators and application in Parity-Time (PT) symmetry

We propose an N-order generalized temporal coupled mode theory (g-TCMT) model, which provides spectral analysis over a wider range for coupled optical resonators with arbitrary coupling coefficients. Using an exemplar system of two, serially coupled micro-ring resonators (MRRs), we demonstrate excellent agreement with the conventional transfer matrix method (TMM). In contrast with the conventional TCMT model, the g-TCMT predicts the existence of a second exceptional point (EP) within a single free spectral range (FSR) for a coupled MRR system with balanced gain and loss, i.e., exhibiting Parity-Time (PT) symmetry.