The beams are oriented in the horizontal plane, at a 45-deg angle to the primary flow direction. Scattering light with the wave vector is collected at a 90-deg scattering angle, collimated by a 150-mm diameter aspheric lens (L1) with 150-mm focal length, shaped into a 20-mm diameter parallel light bundle by a 150-mm diameter aspheric lens (L2) with 500-mm focal length and a lens (L3) with 80-mm focal length, and passed through the Fabry–Perot etalon with 90% reflectivity coatings. The incident and scattering wave vectors are arranged such that the axial component of the jet velocity is measured. In the end, the multibeam interference fringe pattern is imaged onto a high-sensitivity intensified charge coupled device (ICCD) camera with a 300-mm focal length lens, typically, as shown in the Fig. 3 blue dashed circle. Each set of elliptical peaks in the flow interference image corresponds to a different measurement location in the flow. The region of measuring location is about 4 mm in height and 5 mm in length. The spatial resolution of the technique depends on the space interval of each fringe and the laser beam width at the probe volume. The space intervals of fringes are uniform, and the space interval of the fringe in the center is bigger—that is, about 75 pixels window size in processing. The spatial resolution in the experiment is about 0.5 mm in height and better than 0.3 mm in length.