What is a diagram? A symbolic representation of information.
A diagram is a distilled drawing of your idea. Only information that is essential to understanding the concept should be included. Everything else is edited out.
So how can we show ideas, actions, and processes 2-dimensionally? Check out these successful images, and consider how to diagram your Modulator and its effects on light and space:
For more info on how to create a successful diagram, look up Edward Tufte’s series of books: ‘Envisioning Information,’ ‘The Visual Display of Quantitative Information,’ and ‘Visual Explainations.’ http://www.edwardtufte.com/tufte/