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Diffractive beam splitter for laser Doppler velocimetry

1992-09-01, Schmidt, J., Völkel, R., Stork, W., Sheridan, John T., Schwider, J., Streibl, N., Durst, F.

A miniaturized sensor head for the optical measurement of velocities of fluids based on laser Doppler velocimetry is demonstrated. Holographic optical elements mounted on a glass substrate are used for beam splitting and deflection. Volume holograms in dichromated gelatin exhibit good optical efficiency (75% transmission of a cascade of two holographic optical elements). With diffractive devices one can achieve achromatic behavior that makes the sensor insensitive to wavelength drifts or mode hopping of a semiconductor laser.