Direct Writing of 100% Fill-Factor Geometry-Controllable Microlens Arrays with Laser Catapulting

Microlenses and microlens arrays (MLAs) are widely used in various applications, such as lab-on-a-chip, CMOS camera, and solar cells [1] . However, current fabrication methods are restricted to low fill-factor arrays, few geometry options, and flat, often rigid only, substrates. Here, we present a novel additive direct-write method, termed laser catapulting or LCP, for the rapid and customized fabrication of high fill-factor MLAs over a large variety of substrates [2] , [3] . A schematic description of LCP is shown in Fig. 1a . We used a single nanosecond laser pulse to delaminate and catapult, at user-selectable positions, either a single or a multitude of microdisks (up to 260 lenses/mm 2 ) from a donor thin film onto receiver substrate. Following thermal reflow, the printed microdisks are converted into planoconvex microlenses with excellent sphericity and high smoothness ( Fig. 1b,c ). We used as donor a positive photoresist, however, other materials can be transferred in a solid state under appropriate conditions that involve the mechanical and geometrical properties of the selected disk [4] .