Observation of the rotational Doppler shift with spatially incoherent light

The rotational Doppler shift (RDS) is typically measured by illuminating a rotating target with laser prepared in simple, known orbital angular momentum (OAM) superposition. We establish theoretically and experimentally that detecting the does not require incident light to have well-defined OAM spectrum but instead requires correlations within spectrum. demonstrate measurement of using spatially incoherent light.