Special features of local spatial spectrum of Bessel light beams

In this paper we consider the angular spectrum of an apertured Bessel beam when the aperture is circular and shifted laterally with respect to the optical axis. Since the perturbation of the resulting angular spectrum is due to a spatially localized Bessel field, we refer to such an angular spectrum as the local spatial spectrum. We show that the local spatial spectrum of the Bessel beam may differ considerably from the angular spectrum of an unapertured Bessel beam, and find that the ring-shaped angular spectrum is converted into two arcs whose width in the azimuthal direction monotonically decreases as the shift of the circular aperture increases. This phenomenon is predicted theoretically and confirmed experimentally.