Micro-hyperboloid lensed optical fibers for laser chip coupling

Abstract

This study develops a novel approach for producing hyperboloid microlens structure directly on a single-mode optical fiber for high performance diode laser coupling. The hyperboloid shape lensed tip is for matching with the rectangular output of the semiconductor laser diode. The hyperboloid lensed fiber is produced a three-step process including a precision mechanical grinding, a spin-on-glass (SOG) coating and an electrostatic pulling process. A flat-end single mode fiber with the core diameter of 6.6 μm is aligned, fixed and grinded into trapezoid shape. Trace amount of spin-on-glass is applied on the grinded tip and then an electrostatic pulling is used to tune the radius of curvature of around 4.5 μm for the grinded tip. A high coupling efficiency around 80% is obtained while using the produced hyperboloid fibers, which is about double compared to the coupling efficiency of the flat end fiber. The measured coupling stability for 5 individual hyperboloid fibers is 0.116±0.044%, indicating the good coupling stability for the produced hyperboloid microlensed fibers. The developed hyperboloid microlensed fibers provides a solution for direct light coupling between the single mold fiber and the semiconductor diode laser.