Structure of the Book

Structure of the Book

The rest of the book has been divided into four chapters and some appendices. This
first chapter aimed to present an overview of integrated photonic technology, stressing
the radical conceptual change of photonic chips compared to traditional optical systems.
Although several technical terms have been used throughout this chapter (modes,
coupling, TE/TM conversion, etc.) without a rigorous definition, they will be further
studied in subsequent chapters. Chapter 2 gives the basic EM theory necessary for
developing and understanding light behaviour in waveguide structures, starting from
Maxwell’s equations. The theory of optical waveguides is introduced in Chapter 3.
For a correct description of light in waveguide structures having dimensions comparable
to its wavelength, the light must be contemplated as EM waves. Therefore, the
waveguide theory discussed in Chapter 3 is based on the EM theory of light, where
the important concept of optical waveguide mode is introduced. In this chapter we
start analysing the planar waveguide structure, where the most relevant concepts are
explained. Also, once one-dimensional waveguides are studied (planar waveguides), we
focus our attention on the theory of guided modes in two-dimensional structures such
as channel waveguides, which are the basic elements in photonic integrated circuits.
Chapter 4 is devoted to the coupling theory of modes in optical waveguides. The
understanding of mode coupling is of vital importance for most integrated optical
devices. This chapter includes the study of optical power transfer between waveguide
modes, whether it is energy transfer between co-directional or contradirectional propagating
modes. Also, waveguide diffraction gratings are introduced in this chapter, as
they are key integrated photonic elements which offer an efficient and controllable way
of exchange power between waveguide modes.
Finally, Chapter 5 deals with the theory of light propagation in waveguide structures.
The problem of optical propagation in waveguides is reducible to solve light paraxial
propagation in inhomogeneous media, where paraxial means propagation mainly along
a preferential direction. Although we will discuss several approaches to this problem,
we will focus on the beam propagation algorithm, known as beam propagation method
(BPM), which is a step-by-step method of simulating the passing of light through any
waveguiding medium, allowing us to track the optical field at any point as it propagates
along guiding structures.