a la mode: mode matching and beam propagation solutions for MATLAB nicolas smith
It requires MATLAB 2008a, you should add the alm folder to your path (the @ directories should be in a folder that's in your path, but they shouldn't be in the path), or do your work in that folder.
type 'help alm' in MATLAB to begin
example scripts (located in examples/): pslmode.m - showing some basic uses choosecompsexample.m - shows how to use the chooseComponents method beamfitexample.m - uses the beam width fitting function customcostexample.m - shows how to define a custom cost function when optimizing your beam path