Vol. 56, Issue 1, pp. 89-101 (2026)

Abstract

The propagation characteristics of Hermite non-uniformly correlated (HNUC) beams in axisymmetric gradient-index (GRIN) fibers were investigated, revealing the existence of dual focal points along the direction of optical transmission (z-axis) near 0.25L and 0.75L. To exploit this bifocal property, tandem GRIN fibers were employed, with the dual foci positioned within the interstitial gap between the serially connected fibers. Through systematic analysis of the intensity distribution within the gap and the resulting radiation forces on Rayleigh particles, it was demonstrated that the HNUC beam establishes two stable equilibrium points along the z-axis within the gap region, both capable of three-dimensional optical trapping of Rayleigh particles. These findings suggest potential applications in fiber-optic tweezers systems for creating longitudinally distributed multiple optical potential wells.