Third-order nonlinear optical effects (χ3) such as third-harmonic generation and four-wave mixing occur via light-induced modulations of medium parameters such as a refractive index. Since any energy transfer does not occur between light and a nonlinear medium, a third-order nonlinear optical effect is called as parametric process (featured by the fact that quantum mechanical initial and end states are the same). On the other hand, SRS and SBS are nonparametric processes where a part of light energy is transferred to a nonlinear medium.