Fundamental limit for optical components

We show that there is a general limit to the performance of linear optical components, based only on their size, shape, and dielectric constants. The limit is otherwise independent of the design. The mathematics involved applies generally to linear systems with arbitrarily strong multiple scattering. Relevant optical structures include dielectric stacks, photonic crystals, nanometallics, metamaterials, and slow-light structures. The limit also covers acoustic and quantum-mechanical waves, and electromagnetic waves of any frequency. In an example, a one-dimensional glass/air structure, a thickness of at least 41.7 mu m is required for the separation of pulses of 32 different frequencies near 1.55 mu m center wavelength. Larger available dielectric constants would lead to correspondingly shorter limits.