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Published August 2020 | public
Journal Article

Static and dynamic characterization of a focused laser differential interferometer


A focused laser differential interferometer (FLDI) is experimentally characterized via static and dynamic benchtop testing. The static response is probed using a steady, laminar helium jet, and the dynamic response is investigated using an ultrasonic acoustic beam. In the case of the jet, the refractive index field is independently measured using a Mach-Zehnder interferometer operating simultaneously integrated with FLDI. The experimental data for the static response are compared with numerical simulations of the FLDI based on geometric optics and a ray-tracing algorithm, while the dynamic response is compared with an analytical transfer function derived from the same theory. Close quantitative agreement is found between experiment and theory, validating this approach to modeling FLDI performance. Emphasis is given to quantification of the spatial sensitivity of the system which is a key characteristic of FLDI, especially when applied to hypervelocity ground testing facilities where turbulent flow exists in shear or boundary layers outside the core flow.

Additional Information

© 2020 Springer-Verlag GmbH Germany, part of Springer Nature. Received: 30 March 2020; Revised: 9 July 2020; Accepted: 12 July 2020; Published: 05 August 2020. The authors gratefully acknowledge Prof. J. E. Shepherd for all his guidance and interest in this project, as well as providing the laboratory space to perform the experimental work. This work was partially supported by the Office of Naval Research award N00014-16-1-2503 with Dr. Eric Marineau and the Air Force Research Laboratory award STTR FA8651-17-C-0071 with Dr. Daniel Reasor. A preliminary version of this work was presented at, and appears in the proceedings of, the AIAA Scitech 2019 Forum, San Diego, CA.

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