Introduction

As discussed in Chapter 1, nonlinear fibre optics is a very mature field of research, and nonlinear propagation effects have been studied under a wide range of conditions. The basic physical processes that cause spectral broadening in fibres were outlined in Chapter 3, and reference was made to particular mechanisms that contribute to supercontinuum generation.

Whilst it is often convenient to discuss nonlinear spectral broadening in terms of effects that occur in either the normal or anomalous dispersion regime of a fibre, supercontinuum generation is more complex as it involves interactions that generate new spectral components on both sides of the zero dispersion wavelength (ZDW). The aim in this chapter is to extend the description of these interactions given in the preceding chapter in order to illustrate in more detail some commonly observed features of fibre supercontinuum generation. We do not intend to reproduce the comprehensive reviews that already exist in the literature (see the references given in Chapter 3); our objective is rather to provide a succinct overview of supercontinuum broadening mechanisms, and to introduce some of the subject matter that will be considered in more detail in subsequent chapters of the book.

The different regimes of supercontinuum generation can be broadly distinguished by considering short (femtosecond) versus long (picosecond, nanosecond and continuous wave) pump pulses. In this chapter, we consider the general features of supercontinuum generation for three particular commonly-observed cases.