I. Introduction
Over the past two decades, microresonator-generated optical frequency combs have developed into an important emerging technology, with potential applications in metrology and a wide range of other fields [1], [2]. The frequency combs can be generated by coupling continuous-wave laser light into a high-Q microresonator with Kerr nonlinearity to create single solitons, as shown schematically in Figure 1. During the coupling process, there will be a specific transverse mode inside the microresonator that is used to generate the soliton that we will call the coupling mode. A persistent problem in the literature is that the coupling mode being used and its polarization are not identified, which limits the reproducibility of the experimental results. Here, we present a method to determine the coupling mode using published dispersion data and geometric device parameters, accounting for small fabrication or measurement variations. The goal is to help design and characterize microresonator combs. In this work, we focus on the numerical modeling of high-Q microresonators reported in two experimental works [3], [4].