Cost-efficient Aspheric Micro-lenses Manufacturing For High Resolution Imaging Applications

F. Gaillard, V. Reboud, M. Brun, S. Landis
CEA-LETI-Minatec, FR

Keywords: aspheric micro-lens array, high numerical aperture, imprint lithography

Summary:

We report an innovative method to realize stamps to imprint high NA and diffraction limited micro-lens arrays. A new method to fabricate stamp is presented which allows us to process aspheric micro-lenses with curved shape controlled by tuning process parameters during stamp fabrication. Using imprint lithography, polymer micro-lenses arrays stamps are realized at wafer scale in a single step on 8” wafers. Firstly and based on the profiles of the fabricated micro-lens, we have predicted the optical properties using COMSOL software simulations. These simulations data have been compared to experimental results with hemispheric micro-lenses performances as reference showing diffraction limited behavior. In imaging mode, we show that the use of the aspheric micro-lenses is beneficial compared to hemispheric ones in term of small spot size focalization, concentration power. Moreover, NA equal to 0.58 has successfully been obtained with specific polymeric aspheric micro-lens presenting ultra-low surface roughness. Thus, this work opens the way of the realization of cost-effective aspheric optical structures with controlled profiles for various optical applications.