Intracavity Rayleigh-Mie scattering for multipoint, two-component velocity measurement

A simultaneous multipoint, two-component Doppler velocimeter is described. The system uses two optical cavities: a Fabry-Perot etalon and an optical cavity for collecting and recirculating the Rayleigh-Mie-scattered light that is collected from the measurement volume in two parallel but opposite directions. Single-pulse measurements of two orthogonal components of the velocity vector in a supersonic free jet were performed to demonstrate the technique. The recirculation of the light rejected by the interferometer input mirror also increased the signal intensity by a factor of 3.5.