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Quasi-achromatic laser Doppler anemometry systems based on a diffractive beam splitter
Steven Richard Kitchen1, Carsten Dam-Hansen, Michael Linde Jakobsen
1Kamstrup A/S, DK-8660 Skanderborg, Denmark.
Applied Optics
|October 8, 2003
Summary
A novel beam-splitter system enables wavelength-independent operation for laser Doppler anemometry (LDA) using non-stabilized laser diodes. This innovation ensures passive wavelength compensation for fringe spacing, simplifying LDA system design and reducing costs.
Area of Science:
- Optics and Photonics
- Fluid Dynamics Measurement
Background:
- Laser Doppler anemometry (LDA) typically requires stabilized laser sources for accurate measurements.
- Wavelength dependency of beam splitters can complicate LDA system calibration and performance.
Purpose of the Study:
- To develop a wavelength-independent beam-splitter system for LDA.
- To enable the use of non-stabilized laser diodes in LDA systems.
- To achieve passive wavelength compensation for fringe spacing.
Main Methods:
- Designed a beam splitter using two linear diffraction gratings.
- Utilized wavelength-dependent beam spacing for passive compensation.
- Implemented gratings as surface-relief holograms in photoresist for mass production.
- Theoretically and experimentally validated the passive wavelength compensation method.
Main Results:
- Demonstrated a beam-splitter system that is independent of laser wavelength.
- Achieved passive compensation for fringe spacing in the measurement volume.
- Showcased the ability to design desired fringe spacing by adjusting grating distance and lens focal length.
- Confirmed theoretical predictions through experimental validation.
Conclusions:
- The proposed beam-splitter system effectively eliminates wavelength dependency in LDA.
- Non-stabilized laser diodes can be reliably used with this new LDA beam-splitter.
- The system offers a cost-effective and scalable solution for LDA applications through holographic replication.