Nonlinear optical phenomena in subwavelength photonic nanowires

This chapter focuses on the physics needed to design and develop advanced photonic wire devices. It uses as generic example the linear and nonlinear optical properties of silicon photonic wires (SPW). In the first part of the chapter, the geometry and structure of SPWs and the influence of their geometrical parameters on the linear optical properties are described. The interdependence of the photogenerated free carriers and the optical characteristics of SPWs are discussed. In the second part of the chapter, the main physical quantities that describe the nonlinear optical properties of bulk Si are described; e.g., the third-order and Raman susceptibilities, and the frequency dispersion of the effective optical nonlinearities of SPWs, are briefly discussed. The main characteristics of pulse propagation in silicon photonic wire waveguides are presented and discussed in Section 3. The first part of this section is devoted to a derivation of the theoretical model that describes the propagation of single optical pulses in SPWs, followed by an analysis of the main linear and nonlinear optical effects pertaining to the pulse dynamics in SPWs, as well as a discussion of the characteristic lengths associated to these effects. In the second part of this section, we discuss important nonlinear optical effects related to pulse interaction upon copropagation in SPWs, namely cross-phase modulation, modulation instability, and stimulated Raman scattering. The observations here show clearly that SPWs have the potential to form a “fiber-on-a-chip” system allowing for nonlinear optical control of on-chip functions or integrated photonic circuits. Before concluding, we survey a set of material photonic platforms, which can offer alternative solutions to SPWs by providing additional or improved functionality. Among such material platforms we consider silicon carbide, diamond, and compound semiconductor on insulator. The chapter concludes with a summary of the central results of discussion.