Femtosecond-laser wet etch forms low-cost microlens arrays

Polymer micro-optical elements or microlens arrays are typically fabricated using photoresist reflow, photolithography, and LIGA methods that require expensive masks and complex processing steps, or by maskless inkjet and self-assembly processes that limit lens quality. And while laser-direct-writing processes such as two-photon-polymerization (TPP) produce high-quality arrays, the point-by-point fabrication process is extremely slow. Researchers at Xi’an Jiaotong University (Xi’an, China), however, have created a modified laser-direct-writing process that rapidly creates high-quality glass microlens masters that can be used to replicate polymer arrays.

In the process, an 800 nm ultrafast laser delivers intensity- and time-controlled, carefully arranged, individual pulses to a glass slide that is then subjected to wet-etch processing. The laser pulses change the physical and chemical properties of the glass in the focal spots, and the wet-etch processing that follows carves out a unique microlens array pattern. An 80-μm-diameter glass mold with more than 16,000 concave structures can be fabricated in less than three hours, improving significantly on TPP processing and enabling a variety of different glass “master” shapes such as circular, rectangular, diamond, and octagonal designs. Contact Feng Chen at [email protected].