ABSTRACT
The basic principles of optical waveguiding were introduced in Section 2.8. We saw there that waves are guided when they are constrained to lie within a channel between two other media, the refractive index of the channel material being slightly higher than those of the other media, so that the light can ‘bounce’ along the channel by means of a series of total internal reflections (TIRs) at the boundaries between media. The case considered in Section 2.8, and shown again in Figure 8.1, is that where a channel of refractive index n1 lies between two slabs, each with refractive index n2 (n1 > n2); this is the easiest arrangement to analyse mathematically, yet it illustrates all the important principles.
