On-demand longitudinal transformations of light beams via an amplitude-phase-decoupled Pancharatnam-Berry phase element

TL;DR

This paper introduces a novel amplitude-phase-decoupled Pancharatnam-Berry element that enables on-demand longitudinal transformations of light beams, including polarization and topological textures, advancing structured light manipulation.

Contribution

We propose a checkerboard-encoded PB element that overcomes phase-only modulation limits, allowing simultaneous amplitude and phase control for complex beam transformations.

Findings

First demonstration of propagation-transformed optical skyrmions.

Achieved continuous polarization angle variation along propagation.

Enabled on-demand longitudinal transformations of structured light.

Abstract

Overcoming the inherent phase-only modulation limitation of conventional Pancharatnam-Berry (PB) elements, we propose a checkerboard-encoded PB element that enables simultaneous amplitude and phase modulation through PB phase engineering. This single-element platform directly generates polarization-rotating beams with continuously varying polarization angles along the propagation axis, eliminating traditional dynamic phase requirements. By strategically combining the proposed element with a liquid crystal q-plate and waveplates, we demonstrate on-demand longitudinal transformations of polarization states and high-order Poincar\'e sphere beams. Significantly, we achieve, for the first time to our knowledge, the propagation-transformed optical skyrmions, whose topological textures evolve with propagation distance. This amplitude-phase decoupling mechanism and the integration solution for various longitudinal transformations open new avenues in structured light manipulation, particularly benefiting quantum optics and topological photonics applications requiring longitudinal mode control.