Relationship between the superprism effect in one-dimensional photonic crystals and spatial dispersion in nonperiodic thin-film stacks.

We derive that, in all-pass (unity amplitude transmittance or reflectance) one-dimensional layered structures, the tangent of the group-propagation angle, the group delay, and the stored energy are approximately proportional. Thus photonic crystal superprisms and spatial dispersion in nonperiodic photonic nanostructures are generally related to wavelength-dependent stored energy in the stack.