These "writing with light" ideas make me think of GLO IN THE DARK PAPER.

Create a PINHOLE message as seen above in this topic which allows light to "charge" the message into the glo-in-the-dark paper. Enlarge and spread the pinholes out a little more so that you get a good impression on the glow paper.

Alternately, use SUNPAPER that reacts to the light.

Now here's an interesting question: How can we get "light" to write ON US?
God's light is meant to leave an impression on us, to illuminate us, to let US shine.
Hmmmmm.....