(455c) In Search of the Photonic Band Gap

Photonic crystals are materials of mixed dielectric media whose arrangement can cause the reflection of all electromagnetic waves within a range of frequencies, called a complete photonic band gap (PBG). The characteristic length scales of the crystal govern the wavelengths of light affected by a PBG, and so to achieve bandgaps in the visible spectrum colloidal crystals comprised of sub-micron sized nanoparticles have been hotly pursued in the lab. Indeed, the structural color observed in many creatures arises from colloidal crystalline structures on their bodies or wings, creating a PBG. Though first predicted in 1987, and studied in detail in the decades since, design rules dictating all of the necessary and/or sufficient structural features for PBGs are not known. In this talk, we summarize our numerical studies of over 150,000 direct and inverse structures based on templates derived from structures found in crystal databases. We present new design rules, bust some “myths”, and show that the variety of crystal structures with complete PBGs is larger and richer than previously thought. Many of these structures permit large PBGs, even without resorting to large differences in dielectric constants.