TABLE OF CONTENTS The basic concepts and equations of electromagnetic wave theory required for the comprehension of lightwave propagation in optical waveguides are presented. The light confinement and formation of modes in the waveguide are qualitatively explained, taking the case of a slab waveguide. Maxwell s equations, boundary conditions, and the complex Poynting vector are described as they form the basis for the following chapters.
Optical fibers and optical waveguides consist of a core, in which light is confined, and a cladding, or substrate surrounding the core, as shown in Fig. 1.1. The refractive index of the core n 1 is higher than that of the cladding n 0. Therefore the light beam that is coupled to the end face of the waveguide is confined in the core by total internal reflection. The condition for total internal reflection at the core cladding interface is given by n 1 sin( ?/2 ? 
) ? n 0 . Since the angle is related with the incident angle ? by sin 
, we obtain the critical condition for the total internal reflection as
The refractive-index difference between core and cladding is of the order of n 1 ? n 0 = 0 .01. Then ? max in Eq. (1.1) can be approximated by
? max denotes the maximum light acceptance angle of the waveguide and is known as the numerical aperture (NA).
The...
