As contributed by Bro. Brad Newton:
One of the first metaphysical and scientific references to light in modern science and theology is by Robert Grosseteste, ON LIGHT or THE BEGINNING OF FORMS.
In latin with a nice diagram:http://www.fh-augsburg.de/~harsch/Chronologia/Lspost13/Grosseteste/gro_luce.html
English translation is here: