Fabrication of multi-focal chalcogenide glass microlens arrays based on femtosecond laser-assisted chemical etching method

Infrared microlens arrays (IR MLAs) are high-performance optical devices widely used in various applications such as surveillance, medical, industrial and military fields. However, conventional IR MLAs have a single focal plane, which has limitations in capturing targets at different locations. To solve this problem, this paper proposed a method of preparing multi-focal chalcogenide glass (ChG) MLAs using femtosecond laser-assisted chemical etching. The impact of femtosecond laser energy, pulse number and laser focusing position on microlens size, focal length and numerical aperture (NA) were systematically studied. By optimizing the preparation process, multi-focal MLAs with three different focal lengths of -28.3, -25.96, and -21.3 mu m were achieved on Ge-As-S glass, which were tested to have good imaging and focusing effects. Moreover, IR MLAs with NA ranging from 0.52 to 1.15 were obtained by adjusting the laser focus positions. Therefore, the preparation method of MLAs proposed in this work has great flexibility and application potential.