Which materials work best for laser engraving?

When it comes to which materials work best for laser engraving, it can be best summed up with creating contrast. Light-colored woods like alder are ideal because they laser engrave a dark brown. Engraving plastic sheet is another good example that offers high-contrast laser engraving when the top color of the plastic sheet is ablated by the laser to reveal the color layer underneath.

   —Coherent