Hybrid integration of polymer microlens with VCSEL using drop-on-demand technique

Polymer microlens fabrication techniques that enable easy integration with VCSELs are presented. We have developed a high-tolerance coupling structure with microlenses formed on both sides of the optical components for inter-chip optical interconnections, and have developed two types of drop-on-demand techniques for producing microlenses: an ink-jetting method and a dispensing method. Both methods use the surface tension of liquid UV-curable epoxy polymer. We have fabricated various microlenses that have a geometrical diameter from 20 mu m to over 1 mm with F/1 to F/12 by controlling the volume and viscosity of the droplets and their wettability to the substrate. The measured uniformity in arrayed lenses was within +/-1% in lens diameter and +/-3 mu m in pitch. Examples of how we have integrated microlenses with VCSELs are also presented. An ink-jetted microlens on a VCSEL coupled to a single-mode fiber enabled highly efficient coupling: 4 dB greater than without the microlens. A dispensed microlens on a VCSEL coupled to a multimode fiber increased the coupling efficiency by 20 dB compared to without a microlens. In the multimode case, large tolerances of +/-2 mm in axial misalignment and +/-10 mu m in lateral misalignment were obtained for a coupling loss increase of 1 dB.