Observation of two‐dimensional photonic band behavior in the visible

Nanochannel glasses, containing regular hexagonal closed packed arrays of parallel air cylinders with periods varying from 0.25 to 0.19 μm, are shown to display photonic band‐gap behavior throughout the visible that is consistent with previously published theory. Immersing the glasses in liquids of various refractive indices allowed observation of the buildup of the bands as a function of cylinder dielectric constant.