Boosting quantum efficiency using multi-stage parametric amplification

We develop a numerical simulation to demonstrate increased quantum efficiency that can be achieved by using a second stage, phase matched crystal to convert signal energy to the idler wavelength. A pair of ZnGeP2 crystals with walkoff and pump absorption were simulated leading to a tripling of the idler output energy. The output beam characteristics are close to a Gaussian beam with an M2 around 1.1.