The fabrication and fast replication of out of plane parabolic microlens arrays

• Fabrication of an aspherical microlens array using tilted lithography of SU-8;
• Fast replication of the microlens array using the SU-8 lens array as master mold and a PDMS intermediate mold;
• The fabricated microlens array is out-of-plane.

In recent years, aspherical lenses with controllable curvature have become one of the most popular research subjects because of their advantages in eliminating aberration. In this paper, we report a new method of fabricating and replicating aspherical microlens array with their primary optic axes in parallel with the substrate surface. The technology was based on ultra-violet (UV) lithography of SU-8 thick resist. The technology was used previously to fabricate ball lenses in the past and had faced difficulty to make aspherical microlenses. By controlling the mask pattern and other process parameters, especially the exposure dosage, aspherical microlenses with different sizes and surface curvatures were obtained. After replication with PDMS casting, followed by molding of UV light-sensitive material NOA 73, microlenses with much better optical properties were obtained. Because microlenses made using this technique have their main optical axes in parallel with the substrate, they can be easily integrated with other components to form on-chip optical platforms such as optical switch and the imaging systems.