Collapse dynamics of structured optical field in Kerr medium with chirality modulation

Introduction Based on the two-dimensional coupled nonlinear Schrödinger equation, we systematically investigate the collapse dynamics of vector optical fields (VOFs) in a chiral-Kerr medium, where chirality is induced by the unequal refractive indices of left- and right-circularly polarized components. Methods The critical power for VOF collapse is derived analytically using the moment method. Results and Discussion Numerical simulations reveal that the number, locations, propagation distances, and profiles of collapse events are determined by the real and imaginary parts of the chiral refractive indices, the initial power, and the polarization topological charge m . In an achiral Kerr medium, collapse occurs symmetrically. Circular birefringence (CB), i.e., a difference in the real parts of the refractive indices, induces rotation of the state of polarization (SoP) while preserving symmetric collapse positions about the coordinate axes. For a locally linearly polarized VOF, the number of collapse points equals 4×⌈ m /2⌉. For a hybrid polarized VOF under CB, the beam differentiates into 4 m collapse points. In contrast, circular dichroism (CD), arising from a disparity in the imaginary parts, triggers linear-to-elliptical/circular polarization conversion and shifts the collapse positions, with the rotation direction dictated by the relative magnitudes of n + and n −. Under low and high initial powers, the hybrid polarized VOF ultimately splits into 2 m beamlets concentrated at regions of dominant handedness under CD. The rotation angle of the collapse positions with respect to the Y-axis is π/(4 m ). These findings establish chiral-Kerr media as a promising platform for controlling vector field collapse and polarization dynamics, with potential applications in chiral sensing, nonlinear optics, and structured light manipulation.