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(R) 182 silicone elastomer (made by Dow Corning(R)) 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 SiO(2) 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 SiO(2), have even smaller shrinkage while maintaining low intrinsic loss because of the small size of the SiO(2) particles.