Figure 4
From: Enhancement of Doppler spectroscopy to transverse direction by using optical vortex
The azimuthal Doppler shift extracted in \(\phi\) direction from Fig. 3a. The black symbols and the red line show the experimentally measured shift and the fitted sinusoidal curve, respectively. The transverse flow velocity is obtained from the amplitude of the sinusoidal variation of the azimuthal Doppler shift.
