Arbitrary Engineering of Spatial Caustics with 3D-printed Metasurfaces

TL;DR

This paper presents a method using 3D-printed metasurfaces with compensation phase to engineer customizable, curved caustic fields in free space, enabling advanced applications in beam shaping and microscopy.

Contribution

Introduction of a novel 3D-printed metasurface technique with compensation phase to precisely control and morph optical caustics during propagation.

Findings

Successful fabrication of large-scale metasurfaces via two-photon polymerization.

Ability to preserve or morph caustic patterns during propagation.

Potential applications in microscopy and light-matter interaction studies.

Abstract

Caustics occur in diverse physical systems, spanning the nano-scale in electron microscopy to astronomical-scale in gravitational lensing. As envelopes of rays, optical caustics result in sharp edges or extended networks. Caustics in structured light, characterized by complex-amplitude distributions, have innovated numerous applications including particle manipulation, high-resolution imaging techniques, and optical communication. However, these applications have encountered limitations due to a major challenge in engineering caustic fields with customizable propagation trajectories and in-plane intensity profiles. Here, we introduce the compensation phase via 3D-printed metasurfaces to shape caustic fields with curved trajectories in free space. The in-plane caustic patterns can be preserved or morphed from one structure to another during propagation. Large-scale fabrication of these metasurfaces is enabled by the fast-prototyping and cost-effective two-photon polymerization lithography. Our optical elements with the ultra-thin profile and sub-millimeter extension offer a compact solution to generating caustic structured light for beam shaping, high-resolution microscopy, and light-matter-interaction studies.