Concave microlens arrays through an etching-assisted laser seeding method

Microlens arrays are crucial optical elements in micro-optics. However, their efficient fabrication is difficult. High efficiency and quality cannot be simultaneously achieved using conventional fabrication methods; therefore, we propose a novel and efficient method based on the single-pulse exposure of femtosecond lasers and etching-assisted prototyping. When developing this novel microfabrication method, we systematically reviewed several studies. Furthermore, we employed phase modulation using a spatial light modulator to realize the laser seeding-etching microfabrication method. The phase modulation enabled multi-focus exposure instead of single-focus exposure, realizing parallel fabrication in case of concave microlens arrays. Further, combined with the tuning of relative energy and the spatial arrangement of multiple foci, the morphology and optical parameters of each concave microlens can be controlled. The proposed method fundamentally changes the "point-to-point" scanning strategy adopted in conventional micro-nanofabrications via laser direct writing, which is an efficient and high-quality method for fabricating microarray structures.