Photonic crystals : What's in a name?

E ach year, thousands of papers are published with the phrase “photonic crystal” in the title or as a keyword. Some have questioned whether “photonic crystal” is merely a clever new name for a long-standing field of research that goes back 120 years. After all, wave scattering from periodic structures has been known for a long time. Or does the name represent a distinct physical regime that was only recognized when the name emerged about two decades ago?