In this paper, we study diffraction of a vortex Gaussian probe beam on a two-dimensional (2D) Raman-induced diffraction grating. Both near- and far-field diffraction of a vortex beam is considered. In the near field, quasi-Talbot images occur at specific distances from the grating, which corresponds to the classical Talbot length. Diffraction patterns in the Talbot planes are a periodic 2D array of ring-like vortex beamlets with topological charges (TCs) equal to the illuminating probe beam’s charge. The lateral (off-axis) beamlets consist of several overlapping vortices with the TCs l = 1 and l =−1, and their centers (singular points) are offset relative to each other. It is shown that in the near field the TC is conserved, and the total diffraction field represents a single (global) vortex with an effective TC equal to the charge of the vortex probe beam. In the far field, diffraction patterns are also a 2D array of ring-like local vortices with a period depending on the z coordinate. Their TCs are equal to the charge of the probe field. It is shown that in a far field, the diffracted field’s total TC is also equal to that of the probe field. We demonstrate that by choosing the pump field parameters, one can effectively control the intensity of diffraction orders.

在本文中，我们研究了二维 (2D) 拉曼诱导衍射光栅上涡旋高斯探测光束的衍射。涡旋光束的近场和远场衍射都被考虑。在近场中，准 Talbot 图像出现在距光栅特定距离处，这对应于经典 Talbot 长度。Talbot 平面中的衍射图案是环状涡旋子束的周期性二维阵列，其拓扑电荷 (TC) 等于照射探测光束的电荷。横向（离轴）子束由几个重叠的涡旋组成，其中 TC l  = 1 和l =−1，并且它们的中心（奇异点）相对于彼此偏移。结果表明，在近场中，TC 是守恒的，总衍射场代表单个（全局）涡流，其有效 TC 等于涡流探测光束的电荷。在远场中，衍射图案也是环状局部涡旋的二维阵列，其周期取决于z坐标。它们的 TC 等于探测场的电荷。结果表明，在远场中，衍射场的总 TC 也等于探测场的总 TC。我们证明，通过选择泵场参数，可以有效地控制衍射级的强度。