Polarization properties of vector vortices on randomly roughened surfaces

Abstract

Vector vortex beams not only exhibit unique polarization phase characteristics but also carry orbital angular momentum (OAM), making them widely applicable in fields like optical communication and optical microscopy. In addition, studying the scattered light field from random rough surfaces can provide insights for object recognition. Considering polarization effects in the reflection of light from randomly rough surfaces enabled more accurate modeling of the physical processes governing light propagation. This study presents a simulation model for the light field reflected by a vector vortex beam after interaction with a randomly rough surface. A comparative analysis of the peak distribution patterns of the reflected light field was conducted across different polarization states, topological charges, surface roughness, and materials. The simulation results demonstrate that azimuthally polarized vortex beam (APVB) are the least susceptible to perturbations induced by rough surfaces; remarkably, the beam spot symmetry remains at 91.98 % even at a substantial roughness of σ  = 20 μm. Specifically, APVB characterized by a topological charge of l  = 0 and a polarization order of m  = 1 exhibit superior spatial stability. Conversely, when the condition m  =  l is met, the beams undergo a singularity-weakening effect, which precipitates a pronounced spatial broadening of the intensity profile. An experimental optical system based on the Stokes parameter method was designed to measure the polarization degree of APVB light with l  = 0 and m  = 1 reflected from the surfaces of materials such as silica, aluminum and steel. The results demonstrate that a surface roughness of σ  = 1.5 μm, the degree of polarization (DOP) of the reflected light field from the SiO ₂ surface precipitously drops to 0.15. The DOP of the beam reflected from the Al surface maintains a relative stability of approximately 0.48, even at an equivalent or higher roughness ( σ  = 2.1 μm). Ultimately, the theoretical framework and empirical data presented in this study provide a robust foundation for advancing optical target detection and material recognition technologies.