Polarization-Modulated Patterned Laser Sculpturing of Optical Functional Hierarchical Micro/Nanostructures

Abstract

Hierarchical micro/nanostructures have garnered considerable attention for their capabilities in light modulation, but the flexible fabrication of designed optical functional structures at both micro and nano scales remains challenging. Here, a polarization-modulated patterned laser ablation method complemented by flowing liquid is proposed to fabricate hierarchical microgrooves featuring tunable cross-sections and engraved surface nanostructures with controllable periods and orientations. The liquid-assisted ablation counters the shielding effect of ablation debris through laser-induced microjets, ensuring accurate control of the microgroove's shape by modulating the laser pattern in the focal plane. Simultaneously, the absence of debris also permits the consistent formation of laser-induced periodic surface structures (LIPSS) across the microgrooves. The LIPSS's period and orientation can be finely adjusted by manipulating the pulse energy and polarization within the patterned laser spot, facilitating the adaptable creation of hierarchical micro/nanostructures for optical application needs. As a demonstration, blazed gratings featuring orientation-customized LIPSS are fabricated, which exhibit polarization-dependent diffraction efficiency. The laser fabrication technique offers a highly versatile solution for sculpturing shape-controllable hierarchical gratings on hard-to-machine materials, paving the way for the swift production of customized optical elements.