We report what is to our knowledge the first all-optical detection of the frequency beats between Gaussian and Laguerre–Gaussian LG<sub>0</sub><sup>1</sup> modes in their axial superposition, caused by the rotational Doppler effect. The relation between the observable off-axis optical vortex rotation and the rotational frequency shift of the Laguerre–Gaussian component is ascertained. The results can be used as a physical basis for recognition of Laguerre–Gaussian mode spectra along their orbital angular momenta.
© 2003 Optical Society of America
I. V. Basistiy, V. V. Slyusar, M. S. Soskin, M. V. Vasnetsov, and A. Ya. Bekshaev, "Manifestation of the rotational Doppler effect by use of an off-axis optical vortex beam," Opt. Lett. 28, 1185-1187 (2003)