Rapid fabrication of microlens arrays on PMMA substrate using a microlens array by rear-side picosecond laser swelling

Microlens arrays were fabricated on polymethyl methacrylate (PMMA) substrate using a microlens array (MLA) with rear-side ps laser swelling in this study. The modified beam energy can ensure the fabricated microlenses are uniform. Using the foci of a microlens array (MLA), approximately 630 microlenses were fabricated with a single series of pulses, which provides greater processing throughput compared to point-to-point direct laser writing. The formation of smooth microlenses is attributed to photolysis of methyl red (MR) and molecular relaxation. The dependence of height and diameter of the microlenses on laser fluence and irradiation time were investigated. The results show that the size of microlenses could be controlled using the appropriate fluence and irradiation time. Finally, an array of mirolenses with high uniformity was fabricated over a large area. The diameter and height of the microlenses were measured to be 55 and 12 µm, respectively.