Automation of active quadrangular pyramid-shaped fiber endface polishing method

A high-power laser diode (LD) has an elliptical mode field at the endface of its laser diodes. A mode field mismatch between the high-power LD and single-mode fibers (SMFs) results in low coupling efficiency. Accordingly, various methods for coupling between the LD with the higher aspect ratio and SMFs have been employed. Among these approaches, the quadrangular pyramid-shaped fiber endface (QPSFE), which has the capability to control both axial curvatures, can easily match the far field of the high-power LD. However, a QPSFE, which was fabricated by polishing techniques, is hard to employ because of the special shape involved and the need for high precision. This paper presents a novel method for automating QPSFE polishing based on a thorough system analysis and using an online image inspection system. The system successfully supported automatic polishing with an encouraged fiber tip offset that ensures high coupling efficiency. Such an automatic polishing system can also be applied to any other type of fiber endface