Single-Shot Laser Additive Manufacturing of High Fill-Factor Microlens Arrays

High fill-factor microlens arrays (MLA) are key for improving photon collection efficiency in light-sensitive devices. Although several techniques are now capable of producing high-quality MLA, they can be limited in fill-factor, precision, the range of suitable substrates, or the possibility to generate arbitrary arrays. Here, a novel additive direct-write method for rapid and customized fabrication of high fill-factor MLA over a variety of substrates is demonstrated. This approach uses a single laser pulse to delaminate and catapult a polymeric microdisc from a film onto a substrate of interest. Following a thermal reflow process, the printed disc can be converted into a planoconvex microlens offering excellent sphericity and high smoothness (R-RMS < 40 angstrom). Importantly, the transfer of solid microdiscs enables fill-factors close to 100%, not achievable with standard direct-write methods such as inkjet printing or microdispensing. Arbitrary generation of MLA over flexible and curved surfaces, with microlenses presenting a curvature ranging from 20 to 240 mu m and diffraction-limited performance, is demonstrated. The ease of implementation and versatility of the approach, combined with its potential parallelization, paves the way for the high-throughput fabrication of tailored MLA directly on top of functional devices.