Microlens arrays for optoelectronic devices

This paper reports on an improved method of fabricating microlens arrays using a low cost replication process. An accurate negative reproduction ("mold") of an existing high quality lens surface (master) is made in a soft silicone elastomer. This mold is formed by thermally curing Sylgard® 182 silicone elastomer (made by Dow Corning®) on the lens surface. To prevent distortion of the replica surface, the mold is made on a rigid backing plate. Dispensing a commercial epoxy 'Polyset' PCX 28-91B into the mold and curing it under UV radiation generates a replica lens array. The epoxy material is chosen to have minimal shrinkage upon curing. The epoxy material is also chosen to have lower intrinsic loss and have a refractive index tailored to the application. In addition, we have developed a procedure to enable the incorporation of commercially available SiO₂ nanoparticles (Nissan IPA-ST-S, 9-11 nm) into this epoxy material. The incorporation of nanoparticles allows the epoxide to be harder, have a refractive index closer to SiO₂, have even smaller shrinkage while maintaining low intrinsic loss because of the small size of the SiO₂ particles.