An optimum approach for fabrication of tapered hemispherical-end fiber forlaser module packaging

Comprehensive measurements of the dependence of coupling efficiency and rad ius of curvature on taper angle in a tapered hemispherical-end fiber (THEF) for coupling between laser diodes and single-mode fibers are presented. Th e THEF was fabricated by etching the fiber end in a hydrofloride (HF) solut ion with a thin layer of oil floating on top of the HF, and then heating in a fusion splicer to form a hemispherical end. The results show that THEFs with larger taper angles fabricated by greater oil density exhibit a smalle r radius of curvature, and hence a better coupling efficiency. The results of this investigation have led to an optimum approach for high-yield and hi gh-volume fabrication of THEFs that is suitable for use in commercial laser diode modules for efficient coupling between laser diodes and single-mode fibers. The calculation of the effect of oil density in HF etching solution on taper angle based on a semiempirical model. is in good agreement with t he measured results.