High-quality customized micro-diffractive optical devices fabricated from ZnS ceramics using femtosecond laser direct writing and solution etching

Abstract

Zinc sulfide (ZnS) is one of the most widely used materials in infrared optics. ZnS-based micro-optical elements can transform a single infrared material into a functional micro-optical system, showing significant potential in the infrared field. In this study, we report, to the best of our knowledge, the first successful fabrication of surface-etched ZnS ceramic micro-optical devices with acceptable optical quality using femtosecond laser direct writing and subsequent solution etching. We investigated the widths and depths of the fabricated ZnS ceramic microstructures by varying laser energy, repetition frequency, and scanning speed. Based on these data and using the proposed technology, we prepared a series of micro-optical devices, including one- and two-dimensional gratings with various duty cycles, as well as square, circular, and Dammann gratings. Furthermore, the data on width and depth were used to design regulated micro-optical devices with different structural sizes. For example, we constructed a Fresnel zone plate with eight odd and eight even zones, each with different widths and radii. The results show that the fabrication error can be kept below 1 μm. Additionally, the diffraction and focusing results of the gratings demonstrated acceptable optical performance of these ZnS-based micro-optical devices at 632.8 nm and 3 μm, which shows the working ability at visible-infrared wavelengths. This study presents a novel approach for fabricating ZnS micro-optical devices, which could advance the development of infrared micro-optical elements.