FIMMWAVE now includes a sophisticated algorithm which we have termed the Molab (for mode list auto builder), fully automating the finding of eigenmodes. The Molab interface is simple and flexible, so that you can just say “first 3 TE modes please” or “all modes with an effective index between 3.14 and 3.0” etc. The Molab all but guarantees to find all the optical modes of a structure, including some of the most difficult structures such as devices with degenerate modes. So for example, a structure which has a TE and a TM mode that have near identical propagation constant are found without resorting to ridiculously fine search grids. The Molab does not yet work with complex refractive indexes.