Achromatic laser Doppler anemometry based on diode-pumped fiber lasers and diffraction grating beam splitters

Abstract

We present a novel laser Doppler anemometer concept that combines a high portability and compactness with a high optical power. The LDA system is based on the application of a novel light source, a diode-pumped double-clad fiber laser. Besides the high fundamental mode power of currently up to 32 W, fiber lasers have several advantages, like the reliable and simple design, the high efficiency and the compatibility with fiber optic components. Since the beam splitting is accomplished by a diffraction grating, a wavelength independent achromatic LDA calibration constant is achieved. Hence, even powerful fiber lasers, having a broadband emission spectrum can be used for precise LDA measurements. Furthermore fiber lasers are suitable for the implementation of a novel directional discrimination of the velocity measurement without having to involve additional frequency shift elements. In consequence, a simplified directional LDA system can be realized.