Multimode optical parametric amplification in the phase-sensitive regime

TL;DR

This paper investigates optimal multimode phase-sensitive optical parametric amplification, demonstrating experimentally that tight focusing of the seed beam enhances amplification, with implications for quantum imaging and spectroscopy.

Contribution

It introduces a new method for multimode phase-sensitive amplification using tight focusing, validated through experiments, advancing quantum sensing techniques.

Findings

Tight focusing of the seed enhances phase-sensitive amplification.

Optimal multimode amplification can be achieved in the near field.

The method is applicable to quantum-enhanced spectroscopy.

Abstract

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