Self-Healing and Speckle Characteristics of Bessel–Gaussian Beams for Free-Space Optical Communication

Abstract

We experimentally generated Bessel–Gaussian (BG) beams and systematically investigated their self-healing behavior and speckle characteristics under a variety of conditions. To examine speckle formation, the beams were scattered, resulting in both diffracting and non-diffracting Bessel speckles, which were analyzed in the near-field as well as in the Fourier-transformed far-field. The non-diffracting nature of the beams was confirmed for both fully coherent and partially coherent illumination, highlighting the influence of spatial coherence on beam propagation and speckle stability. The topological charge of the BG beams, a key parameter defining their orbital angular momentum, was measured using a Mach–Zehnder interferometer; forked interference fringes in the interferograms provided a direct visualization of the beam’s topological charge. To study the self-healing property, geometric obstructions were introduced in the beam path, revealing that the recovery distance increases with the size of the obstacle but decreases with the axicon parameter. Additionally, the recovered intensity was found to diminish with larger obstructions, indicating a practical limit to the beam’s self-reconstruction capability. These results demonstrate the robustness of BG beams, underscore their potential for applications in optical manipulation, high-resolution imaging, optical trapping, and free-space optical communication, where stability and recoverability of the beam are crucial.