Conformal frequency conversion for arbitrary vectorial structured light

TL;DR

This paper introduces a conformal frequency conversion method that preserves the complex spatial and polarization structure of vectorial structured light during nonlinear frequency conversion, enabling advanced optical applications.

Contribution

A novel conformal frequency conversion scheme that maintains the full spatial and polarization structure of vectorial structured light during nonlinear processes.

Findings

Demonstrated polarization-independent sum-frequency generation

Preserved the spatial topological structure of vectorial light

Enabled potential applications in multimodal communication and quantum imaging

Abstract

Vectorial structured light with spatially varying amplitude, phase, and polarization is reshaping many areas of modern optics, including nonlinear optics, as diverse parametric processes can be used to explore interactions between such complex vector fields, extending the frontiers of optics to new physical phenomena. However, the most basic nonlinear application, i.e., frequency conversion, still remains challenging for vectorial structured light since parametric processes are polarization dependent, leading to a change in the spatial topological structure of signals. In this work, to break this fundamental limit, we propose a novel conformal frequency conversion scheme that allows to maintain the full spatial structure of vectorial structured light in the conversion; and systematically examine its spatial polarization independence based on non-degenerate sum-frequency generation with type-0 phase matching. This proof-of-principle demonstration paves the way for a wide range of applications requiring conformal frequency conversion, and, particularly, to implement frequency interfaces with multimodal communication channels, high-dimensional quantum states, and polarization-resolved upconversion imaging.