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This study develops improved mathematical models for thermal noise in Michelson interferometers operating at high frequencies (MHz range), where traditional approximations break down. The researchers created more accurate models for five types of thermal noise—substrate and coating mechanical noise, substrate and coating thermoelastic noise, and coating thermorefractive noise—that are relevant when quantum shot noise is suppressed through advanced readout techniques like photon counting. The models were validated against existing low-frequency predictions and experimental data from the Holometer experiment, then applied to design the GQuEST experiment currently under construction.
Why it matters
As gravitational-wave detectors and other precision optical instruments adopt quantum metrology techniques that reduce shot noise, thermal noise becomes the limiting factor for sensitivity. These improved models enable more accurate characterization of weak, high-frequency signals and better design of next-generation interferometers, optical clocks, and optomechanical sensors operating in previously inaccessible frequency regimes.
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⚠️ Preprint – Noch nicht peer-reviewed
Dieser Artikel wurde noch nicht von unabhängigen Experten begutachtet. Die Ergebnisse sind vorläufig und sollten mit Vorsicht interpretiert werden.
Abstract: Thermal noise in optics constrains the precision of optical experiments, including Michelson interferometers, optical clocks, and optomechanical sensors. While high-power optical experiments such as gravitational-wave detectors are currently limited mainly by quantum noise, new experiments incorporating recent insights from quantum metrology are being developed that evade the quantum shot noise background. In particular, Michelson interferometers that use photon-counting readout will look for weak, high-frequency signals. Since shot noise is no longer the dominant noise source with these readout schemes, it is important to accurately model thermal noise to characterize signals and design more sensitive experiments. However, previous modeling uses approximations that are no longer valid in these frequency regimes. In the MHz band, the quasistatic approximation does not apply. We therefore develop more general models of substrate and coating mechanical (Brownian) noise, substrate and coating thermoelastic noise, and coating thermorefractive noise. We validate the models with comparisons to previous low-frequency modeling and high-frequency spectra from an experiment that has already taken data, the Holometer. We then apply the new models to GQuEST, an experiment under construction.
Source: High-Frequency Thermal Noise in Michelson Interferometers