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Wavelength calibration of birefringent interferometers for 2-D measurement of plasma flow

Allcock, Joseph S.; Silburn, Scott A.; Sharples, Ray M.; Harrison, James R.; Conway, Neil J.; Long, Ting; Lin, Nie

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Authors

Joseph S. Allcock

Scott A. Silburn

James R. Harrison

Neil J. Conway

Ting Long

Nie Lin



Abstract

Imaging birefringent interferometers are used to measure plasma flow in 2-D via the Doppler shift of a spectral emission line. Applications include plasma physics study in fusion energy experiments and in the Earth’s upper atmosphere. We present a new, to the best of our knowledge, method for wavelength calibration that does not require measurement at the rest wavelength of the targeted spectral line, nor measurement using a tuneable laser source. This is useful when such light sources are not available. Fringes measured at known wavelengths from the emission lines of gas-discharge lamps are used to constrain an instrument model which can generate the required calibration data. In the process, optical path difference, dispersion and misalignments are characterized. The “2π ambiguity” of interferogram phase data is handled using circular statistics, allowing the wavelength span of the calibration lines to far exceed the unambiguous measurement range of the instrument. The technique is demonstrated to an accuracy of ±1 pm (±0.7 km/s flow-equivalent) over a 40 nm visible wavelength range.

Citation

Allcock, J. S., Silburn, S. A., Sharples, R. M., Harrison, J. R., Conway, N. J., Long, T., & Lin, N. (2023). Wavelength calibration of birefringent interferometers for 2-D measurement of plasma flow. Optics Express, 31(2), 1901-1915. https://doi.org/10.1364/oe.473278

Journal Article Type Article
Acceptance Date Dec 8, 2022
Online Publication Date Jan 6, 2023
Publication Date 2023
Deposit Date May 31, 2023
Publicly Available Date Jun 6, 2023
Journal Optics Express
Publisher Optica
Peer Reviewed Peer Reviewed
Volume 31
Issue 2
Pages 1901-1915
DOI https://doi.org/10.1364/oe.473278

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Publisher Licence URL
http://creativecommons.org/licenses/by/4.0/

Copyright Statement
Published by Optica Publishing Group under the terms of the Creative Commons Attribution 4.0 License. Further distribution of this work must maintain attribution to the author(s) and the published article's title, journal citation, and DOI.





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