A novel method to fabricate lensed optical fiber with SU-8 photoresist for efficient coupling to high-power laser diodes

A new scheme of non-spherical cone-shaped microlens employing an innovative fabrication technique for efficient coupling between the high-power IR laser diodes and the gradient-index fibers is proposed. A novel process is developed to apply SU-8 on the fiber tip utilizing surface tension force and to form the cone-shaped micro-lens structure using electrostatic pulling method at a temperature of 60degC. Microlens with various radius of curvature can be easily produced by tuning the applied electric fields during the electrostatic pulling process. The measured coupling efficiency is up to 75% for coupling a 1310-nm laser diode chip while using the fabricated lensed optical fiber (R = 62 mum), which is around 1.88-fold higher than the coupling efficiency of a flat-end fiber. The proposed method is feasible of producing high-quality lensed optical fibers in a high throughput and low-cost way.