SCG Involving Second-Order Nonlinearity

This chapter will discuss the SCG including second-order nonlinearities. We start from fundamental equations and concepts, which could provide a framework to understand second-order nonlinear effects involved in the SCG process. The equations and concepts of second-harmonic generation (SHG), sum-frequency generation (SFG), and difference frequency generation (DFG) are provided to deepen the understanding of the SCG process. In addition, we summarize the representative results of SCG based on second-order and third-order nonlinearities, and SCG only based on second-order nonlinearity.