ABSTRACT
This chapter discusses the underlying physical principles responsible for second-order nonlinear optical processes and derive the fundamental equations governing parametric generation in anisotropic, nonlinear media. It considers the propagation of electromagnetic waves within an anisotropic nonlinear medium. Traditional methods for the generation of such radiation are based on the stimulated emission between quantised energy levels in conventional atomic or molecular laser gain media with extended fluorescence bandwidths. In media where the quantised levels are sufficiently broadened to form continuous bands, tunable emission can result from transitions between such bands. The coupled wave equations can be used to obtain the equations governing parametric amplification and gain in a nonlinear medium. The exact solutions to these equations are involved, but in a limiting case that demonstrates the essential features of parametric amplification, it is assumed that the pump wave maintains constant amplitude throughout the interaction region.
