Application of diode-pumped fiber lasers for laser Doppler anemometry

摘要

Diode-pumped fiber lasers emit today more than 30W of fundamental mode power. Due to their compact realization at low costs, they are attractive for portable high power laser Doppler anemometers (LDA). We present the state-of-the-art of fiber lasers with emphasis on Nd:glass fiber lasers with high power emission in the infrared and up-conversion fiber lasers with visible emission wavelengths. The LDA system is realized by using a phase diffraction grating as a beam splitter. An achromatic LDA system is shown, which enables the employment of high power fiber lasers having large emission line widths. Diffraction optics was used for the realization of a miniaturized fiber-coupled LDA measuring head. The directional discrimination of the achromatic LDA system was achieved by an acousto-optical modulator as both a diffractive beam splitter and as a frequency shifter.