Photochemically Engineered Large-Area Arsenic Sulfide Micro-Gratings for Hybrid Diffractive–Refractive Infrared Platforms

The cover picture referring to article number 2300241 by Myungkoo Kang, Tian Gu, and co-workers showcases photochemically induced micro-gratings for a hybrid diffractive–refractive lens. These lenses, composed of diffractive and refractive elements, aim to achieve achromatic optics with significantly reduced size, weight, and power consumption. Here, metastable As₂S₃ chalcogenide glasses underwent direct laser writing and subsequent selective etching to create diffractive micro-gratings. The grid on the lens’ surface represents photochemically induced micro-gratings, while the surrounding residue indicates ongoing selective etching. Incident parallel beams converge into a single focal point upon passing through the lens. (Cover illustration: courtesy of Ella Maru Studio.)