Photonic Crystals

Abstract

In the previous chapters of this text we have explored how light can be guided by high index regions of a dielectric. Many types of waveguide were examined, including graded index slabs, circular step-index fibers, and rectangular ridge structures. In all of these cases we found that light can be guided by high index regions and as a result can go around bends, couple to other waveguides, and be manipulated to perform certain functions. The guiding mechanism in all cases arose from the “attraction” light has toward higher index regions. We described this attraction in a variety of terms, including total internal reflection, the eikonal equation, or spatial resonances forming from reflections on index changes, but in all cases the basic mechanism is the same: higher index regions of a dielectric act like a “potential well” for light, and so long as things change slowly (bends are gentle, or dimensions vary slowly), light tends to remain trapped in that potential well.