is strongly depleted . Under these conditions, the overall
Conversion efficiency and output power (Gaussion beams). The results given above are modified for real optical beams with radial intensity dependence. Bjorkholm  has treated this case for a “nearly plane wave” pump beam. The meaning of this phrase is that the spatial intensity variation over the beam cross-section is slow enough that the generated signal and idler beams can effectively be divided into independent beamlets of nearly uniform intensity and planar phase over the interaction length of the beams. A uniform plane wave
Figure 7 DRO conversion efficiencies, (a) Plane wave and Gaussian beam results for a simple DRO. (b) Plane wave and Gaussian beam results for a DRRO.