Nonlinear Photonics

All-optical modulation of an optical wave is accomplished through a nonlinear optical process that involves one or multiple optical waves. A nonlinear optical modulator can be based on either self-modulation or cross-modulation. Such nonlinear optical modulators and switches are also known as all-optical modulators and all-optical switches, respectively. Most all-optical modulators and switches are based on third-order nonlinear optical processes, but some rely on the high-order process of optical saturation, either absorption saturation or gain saturation. There are two fundamentally different types of all-optical modulators and switches: the dispersive type and the absorptive type. All-optical modulation of the dispersive type, which is based on the optical Kerr effect, is discussed in this chapter. In the first four sections, the physics, phenomena, and measurement of the optical Kerr effect are discussed. The last two sections cover all-optical modulators and switches in the bulk form and those in the waveguide form.