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Updated: Dec 25, 2025
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The Generation of Higher-order Laguerre-Gauss Optical Beams for High-precision Interferometry
Published on: August 12, 2013
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Two-point, parallel-beam focused laser differential interferometry with a Nomarski prism.
Applied Optics
|April 1, 2020
Summary
This study introduces a new method using a Nomarski prism and laser interferometer to precisely measure density disturbance velocities. The technique allows simultaneous measurements at two points, minimizing bias for accurate fluid dynamics research.
Area of Science:
- Fluid Dynamics
- Optical Measurement Techniques
- Aerodynamics
Background:
- Measuring phase velocity of density disturbances is crucial for understanding fluid flow phenomena.
- Existing methods may face limitations in spatial resolution and susceptibility to external influences.
- High-frequency measurements are essential for capturing rapid dynamic events in fluid systems.
Purpose of the Study:
- To develop and demonstrate a novel instrument for measuring the phase velocity of density disturbances.
- To enable simultaneous, spatially resolved measurements of density fluctuations.
- To minimize measurement bias from off-plane density variations.
Main Methods:
- Utilized a Nomarski polarizing prism integrated with a focused laser differential interferometer.
- Enabled simultaneous measurement of density disturbances at two closely spaced, arbitrarily oriented points.
- Achieved high sampling frequencies (≥10 MHz) with minimized bias due to parallel beam propagation.
Main Results:
- Successfully measured the phase velocity of a spark-generated shock wave in a laboratory setting.
- Quantified the phase velocity of a second-mode instability wave on a cone model in Mach 6 flow.
- Results were validated using high-speed schlieren imaging.
Conclusions:
- The Nomarski prism-based laser interferometer is a high-performance instrument for accurate density disturbance velocity measurements.
- The method provides simultaneous, spatially resolved data with reduced bias.
- Demonstrated applicability in both shock wave and supersonic flow instability studies.
