A new nonintrusive velocimetry diagnostic that combines the sensitivity of frequency-modulated (FM) absorption spectroscopy techniques and the spectral discrimination afforded by atomic-vapor absorption filters is presented. Doppler-shifted light from a FM Ti:sapphire laser scattered from a supersonic flow is imaged through a potassium-vapor cell and is detected by FM spectroscopy. The difference between the potassium resonance frequency and the laser frequency when the scattered light is in resonance is the flow-induced Doppler shift.
© 1997 Optical Society of America
J. H. Grinstead, N. D. Finkelstein, and W. R. Lempert, "Doppler velocimetry in a supersonic jet by use of frequency-modulated filtered light scattering," Opt. Lett. 22, 331-333 (1997)