Diffraction of Bessel beams on 2D amplitude gratings -- a new branch in the Talbot effect study
In this paper, an analytical theory for the diffraction of a Bessel beam of arbitrary order $J_l(κr)$ on a 2D amplitude grating is presented. The diffraction pattern in the main and fractional Talbot planes under certain conditions is a lattice of annular microbeams, the diameters of which depend on the grating period, the illuminating beam diameter, the number of the Talbot plane, and the topological charge $l$. For the rings near the optical axis, the latter reproduces $l$ of the illuminating beam. Experiments carried out on the Novosibirsk free electron laser at a wavelength $λ= 141$$μ$m using gratings with hole diameters of down to $d \approx 2λ$, as well as, the numerical simulations, well support the theory. Since the Laguerre-Gaussian beams can be represented as a superposition of Bessel beams, results of this paper can be applied to the analysis of the Talbot effect with the Laguerre-Gaussian beams.