Reflowed sol-gel microlens for coupling a laser diode and a single-mode fiber with high efficiency: a cost-effective and high-volume fabrication solution

Abstract

In optical communications and optical interconnects, high coupling efficiency between a laser diode and a single mode fiber is indispensable, while the coupling loss mainly originates from the mismatch of their numerical apertures. In order to improve the coupling efficiency, it is a practical scheme to introduce a refractive microlens between them. Nevertheless, the fabrication of refractive microlens array (MLA) often required complicated lithographic and etching process. Moreover, structural homogeneity and dimensional uniformity of fabricated MLA were difficult to sustain. In this paper, we extend the application of low-cost inorganic-organic SiO₂/ZrO₂ sol-gel glass with a simple reflow technique for fabrication of refractive MLA. The intrinsic advantages of hybrid sol-gel material lay not only as an etch-free single-step fabrication material, but also, its uniformity and other excellent optical properties. The adoption of reflow technique in the fabrication of refractive MLA is much more economical and suitable to mass production as expensive high-energy beam-sensitive gray-scale mask, or etching processes is not required. The fabricated refractive MLA have excellent surface smoothness and dimension uniformity, which can provide high coupling efficiency of a laser diode to a single mode fiber. The proposed microlens coupling scheme has the advantages of low coupling loss, low cost and small package volume.