In this PHD thesis the scalar Fox and Li algorithm for the dominant transversal resonator eigenmode calculation is generalized to a fully vectorial field tracing concept. Therefore Fox and Li’s scalar integral equation is reformulated to a set of coupled operator equations. The introduction of a field tracing round trip operator concept shows that, in principle, any modeling technique which can be formulated to operate for electromagnetic fields can be used to simulate light propagation through the different subdomains of the resonator. This allows a flexible, fast, and accurate simulation of the fully vectorial dominant transversal resonator eigenmode. Several examples are presented to demonstrate the flexibility and accuracy of the field tracing approach.