Chapter 9 - Highly nonlinear fibers

Abstract

The nonlinear phenomena in optical fibers is enhanced considerably in microstructured fibers with micrometer-size air holes within their cladding. This chapter focuses on several important applications of microstructured fibers. Their nonlinear and dispersive properties are discussed in Section 9.1. The next section describes how microstructured fibers can be used for tuning the wavelength of femtosecond pulses over a wide range by exploiting the nonlinear effects, such as stimulated Raman scattering and four-wave mixing. The use of such fibers for generating a supercontinuum (an ultrabroadband spectrum) is discussed in Section 9.3. As the bandwidth of such supercontinua can cover a wavelength range wider than 500 nm, Section 9.3 also covers several applications that fall in areas as diverse as biomedical imaging and frequency metrology. Section 9.4 is devoted to fiber-based frequency combs that have attracted considerable attention since 2010. The applications of photonic-bandgap fibers, whose hollow core is filled with a gas or liquid to enhance the nonlinear effects, are discussed in Section 9.5.