Caustic-Based Modulation of Structured Light Fields along Arbitrary Trajectories

Abstract

This paper presents an English course report on the caustic-based modulation of structured light fields. Starting from the angular-spectrum description of non-diffracting beams, an inverse design strategy is introduced to map a prescribed transverse intensity contour into an annular spectral phase. In this way, the optical caustic becomes the geometric skeleton that governs both the beam profile and its subsequent propagation. The method enables sharply confined structured beams with arbitrary shapes, while an additional synthesized phase term translates the structure along user-defined trajectories in three-dimensional space. Elliptic and heart-shaped beams are discussed as representative examples, showing that the same framework supports both straight and accelerating propagation. Experimental observations reported in the source material verify the numerical predictions and confirm the robustness of the generated beams. Because these structured non-diffracting fields exhibit strong intensity gradients and structured orbital angular momentum, they are promising for optical trapping, particle transport, beam shaping, wavefront control, and deep imaging. The study demonstrates that inverse caustic engineering offers a flexible and physically intuitive route for designing advanced structured light fields beyond conventional Bessel, Mathieu, Weber, and Airy beam families.