Coupled-mode theory of electromagnetism including wide band distributed interactions

Usually the electromagnetic field is naively thought as given by six independent quantities E and B. However in chapter 2 the field was presented as dependent on a four-component vector potential. In this chapter a different approach is formulated, in which electromagnetic field is determined by two scalar complex functions. This approach will serve as a starting point for the following variational analysis given in the next chapter, where the electromagnetic field is shown to depend only on a single complex function.