| 摘要 |
PROBLEM TO BE SOLVED: To couple a semiconductor laser to a single-mode optical fiber at low loss and to facilitate the manufacturing of a coupler in a small size at a low cost. SOLUTION: This is a light source/optical fiber coupler that couples a diffused optical flux outgoing from a light source (e.g. semiconductor laser 10) on the end face of an optical fiber (e.g. single-mode optical fiber 14) through a distributed refractive index type rod lens 12. The distributed refractive index type rod lens has a shape in which the end face on the light source side is a plane and in which the end face on the optical fiber side is a convex, with a numerical aperture NA2 on the light source side at 0.40-0.75, with an effective radius r0 of the lens at 0.3-1.0 mm, and with a radius of curvature R1 of the spherical surface at 1.2-2.0 mm.
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