Maximizing precision in saturation-limited absorption measurements

Jake Biele, Sabine Wollmann, Joshua W. Silverstone, Jonathan C.F. Matthews, Euan J. Allen

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Quantum fluctuations in the intensity of an optical probe is noise which limits measurement precision in absorption spectroscopy. Increased probe power can offer greater precision; however, this strategy is often constrained by sample saturation. Here, we analyze measurement precision for a generalized absorption model in which we account for saturation and explore its effect on both classical and quantum probe performance. We present a classical probe-sample optimization strategy to maximize precision and find that optimal probe powers always fall within the saturation regime. We apply our optimization strategy to two examples, high-precision Doppler broadened thermometry and an absorption spectroscopy measurement of chlorophyll a. We derive a limit on the maximum precision gained from using a nonclassical probe and find a strategy capable of saturating this bound. We evaluate amplitude-squeezed light as a viable experimental probe state and find it capable of providing precision that reaches to within >85% of the ultimate quantum limit with currently available technology.

Original languageEnglish
Article number053717
JournalPhysical Review A
Issue number5
Publication statusPublished - 22 Nov 2021

ASJC Scopus subject areas

  • Atomic and Molecular Physics, and Optics


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