Write down the equations of motion for the signal and idler waves undergoing NOPA, assuming undepleted pump and phase matching

Nonlinear optics In Lecture 11, we analyzed nondegenerate optical parametric ampli cation (NOPA) under the undepleted-pump approximation and assuming no linear loss  for all lightwaves involved. In practice, however, the linear losses could be significant. Let Γs and Γi be the linear loss coefficients per unit length for the signal and the idler waves, respectively, […]