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 60 °C. 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 μm), 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.