Lightwave Engineering

2	Fundamentals of Optical Waveguides

2.1  FREE-SPACE WAVES AND GUIDED WAVES

In contrast to a free-space wave that propagates in a free space (or in a uniform medium) as described in Chapter 1, light that propagates in a confined space limited to a cross-section perpendicular to the direction of propagation is called a guided wave, and the medium to which such light is confined is called an optical waveguide. For example, in a slab waveguide in which a cross-sectional structured transparent dielectric plate of high refractive index is sandwiched by dielectric materials with low refractive index, as shown in Figure 2.1, when light is beamed at an incident angle smaller than the total internal reflection angle from the high refractive index ...