Tunable dual autofocusing of elliptical Airy off-axis vortex beams

Owing to its wide applications in optical imaging, optical data storage, and particle trapping, the dual autofocusing characteristics of extended Airy beams have been extensively studied. However, the relatively fixed dual autofocusing limits its flexibility in practical applications. Herein, we embed an off-axis vortex into an elliptical Airy beam (EAB), construct the elliptical Airy off-axis vortex beam (EAOffVB), and reveal its novel dual autofocusing characteristics. Experimental and theoretical results show that the dual autofocusing performance of EAOffVBs can be easily controlled by adjusting the exponential decay factor a, the radius of the principal ring r₀, the scale factor w₀, the elliptic parameter t, the topological charge l, and the radial position r_k and azimuth angle φ_k of the optical vortex. Compared with the reported methods, although adjusting the elliptical parameter t of the EAB can achieve the control of the relative intensity of two autofocus points, this method inevitably causes a shift in the position of the second focal point. The present work proposes an innovative control strategy: by precisely adjusting the off-axis vortex (r_k, φ_k) in EAOffVBs, flexible control of the relative intensity between two autofocus points can be achieved while keeping the positions of the two points essentially unchanged. Besides, an exemplary application of EAOffVB's dual autofocusing characteristics in topological charge detection is demonstrated. These findings indicate that the EAOffVB has broad potential applications in tasks such as topological charge detection, multi-degree-of-freedom particle manipulation, and optical communication.