Rotating wave packet caused by the superposition of two Bessel–Gauss beams

Abstract

This paper presents, theoretically, a rotating wave packet by overlapping two Bessel–Gauss beams with different longitudinal wave vectors and topological charges. Our results show that the angular velocity of this kind of packet varies with propagating distance, and that Gauss amplitude modulation thus depends strongly on the Fresnel number Nf. In the far field, the angular velocity of the packet tends to zero, so the packet will no longer rotate. If Nf > 3.18, the packet will rotate with a constant velocity or have a stable rotating velocity along the propagation distance. Interestingly, if appropriate Gauss waist size and propagating distance z are chosen so that 0.006 < Nf < 3.18, both the amplitude and the direction of the rotating angular velocity can be manipulated for given topological charges and longitudinal wave vectors. The small Gauss waist radius can induce angular velocity dispersion, causing radial rotation with out-sync and thereby the phase distortion of the BG beam.