A simple method for fabrication of thick sol-gel microlens as a single-mode fiber coupler

We demonstrate a cost-effective and high-volume fabrication method for building microlenses in hybrid sol-gel, material. The fabrication process includes three main steps. First, the microlenses were built in photoresist by reflowing. technique. Second, surface profiles of the microlenses were transferred to an elastic polydimethylsiloxane (PDMS) replica. Finally, the microlenses were fabricated by impressing the replica onto a thick sol-gel film with an ultraviolet curing simultaneously. As an example, a microlens with a diameter of 80 mum and a sag height of 13 mum was fabricated for a coupling experiment between two single-mode fibers. The measured coupling efficiency of 2.2 dB (60%) was obtained, which-could be further improved to approach the theoretical efficiency of 0.3 dB (93%) with an ultraprecision alignment stage.