Multimode optical parametric amplification in the phase-sensitive regime

Phase-sensitive optical parametric amplification of squeezed states helps to overcome detection loss and noise thus increase the robustness sub-shot-noise sensing. Because such techniques, e.g., imaging spectroscopy, operate with multimode light, is required. Here we find optimal methods for phase-sensitive verify them in an experiment where a pumped second-order nonlinear crystal seeded Gaussian coherent beam. obtained by tightly focusing seed into crystal, rather than seeding close-to-plane waves. This suggests that images should be performed near field. Similar recipe can formulated time frequency, which makes this work relevant quantum-enhanced spectroscopy.