Adaptive interferometric velocity measurements using a laser guide star

J. Czarske; H. Radner; L. Büttner

doi:10.1117/12.2186360

17 July 2015 Adaptive interferometric velocity measurements using a laser guide star

J. Czarske, H. Radner, L. Büttner

Proceedings Volume 9524, International Conference on Optical and Photonic Engineering (icOPEN 2015); 95240K (2015) https://doi.org/10.1117/12.2186360
Event: International Conference on Optical and Photonic Engineering (icOPEN2015), 2015, Singapore, Singapore

Abstract

We have harnessed the power of programmable photonics devices for an interferometric measurement technique. Laser interferometers are widely used for flow velocity measurements, since they offer high temporal and spatial resolutions. However, often optical wavefront distortions deteriorate the measurement properties. In principle, adaptive optics enables the correction of these disturbances. One challenge is to generate a suitable reference signal for the closed loop operation of the adaptive optics. An adaptive Mach Zehnder interferometer is presented to measure through a dynamic liquid-gas phase boundary, which can lead to a misalignment of the interfering laser beams. In order to generate the reference signal for the closed loop control, the Fresnel reflex of the phase boundary is used as Laser Guide Star (LGS) for the first time to the best of the authors’ knowledge. The concept is related to the generation of artificial stars in astronomy, where the light transmitted by the atmosphere is evaluated. However, the adaptive interferometric flow velocity measurements at real world experiments require a different concept, since only the reflected light can be evaluated. The used LGS allows to measure the wavefront distortions induced by the dynamic phase boundary. Two biaxial electromagnetically driven steering mirrors are employed to correct the wavefront distortions. This opens up the possibility for accurate flow measurements through a dynamic phase boundary using only one optical access. Our work represents a paradigm shift in interferometric velocity measurement techniques from using static to dynamic optical elements.

Citation Download Citation

J. Czarske, H. Radner, and L. Büttner "Adaptive interferometric velocity measurements using a laser guide star", Proc. SPIE 9524, International Conference on Optical and Photonic Engineering (icOPEN 2015), 95240K (17 July 2015); https://doi.org/10.1117/12.2186360

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KEYWORDS

Adaptive optics

Velocity measurements

Interfaces

Interferometry

Wavefront distortions

Mirrors

Laser Doppler velocimetry

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