At each frequency, one or more modes can be found giving a set of eigenvalues which can be used to construct a band diagram or dispersion relation.

Because guided modes are trapped in the slab, they cannot be excited by light incident on the top or bottom interfaces. Light can be end-fire or butte coupled by injecting it with a lens in the plane of the slab. Alternatively a coupling element may be used to couple light into the waveguide, such as a grating