Interferometer cosine error and uncertainty minimisation using an external cavity

Douglas J. Little; Brady Shearan; John R. Fiander; Yabai He

doi:10.1117/12.3015634

18 June 2024 Interferometer cosine error and uncertainty minimisation using an external cavity

Douglas J. Little, Brady Shearan, John R. Fiander, Yabai He

Proceedings Volume 12997, Optics and Photonics for Advanced Dimensional Metrology III; 129970L (2024) https://doi.org/10.1117/12.3015634
Event: SPIE Photonics Europe, 2024, Strasbourg, France

Abstract

Cosine errors are ubiquitous in measurement science, referring to the proportional error that arises when the measurement device is incorrectly oriented. In the context of interferometry, this error arises when the orientation of the Fabry-Pérot cavity does not line up with the "true" measurement axis. While the cosine error can be corrected for if the degree of misalignment is known, any uncertainty in the misalignment will propagate to the length measurement, hence there is motive to minimise this uncertainty where it limits the overall measurement precision. This paper demonstrates the orientation of a plane-concave Fabry-Pérot interferometer to an external measurement axis using an external optical cavity. The purpose of this external cavity was to create a precise path reference with which to align the retro-reflection from the interferometer's plane mirror. Using this method, an interferometer was oriented relative to the central geometric axis of a calculable cross-capacitor within 8.3 μrad, with this axis defined using a custom sliding quadrant photo-detector centered between its four capacitor electrodes. The precision achieved with this technique is critical for meeting the few nF/F relative uncertainty target for this new capacitor, being built at the National Measurement Institute, Australia, which will ultimately improve the detection of systematic errors between calculable cross-capacitor and quantum-Hall realisations of the SI farad.

Conference Presentation

(2024) Published by SPIE. Downloading of the abstract is permitted for personal use only.

Citation Download Citation

Douglas J. Little, Brady Shearan, John R. Fiander, and Yabai He "Interferometer cosine error and uncertainty minimisation using an external cavity", Proc. SPIE 12997, Optics and Photonics for Advanced Dimensional Metrology III, 129970L (18 June 2024); https://doi.org/10.1117/12.3015634

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