| 摘要 |
<p>An excitation fiber (110) having a first segment (110A) and a second segment (110B). The second segment has a smaller refractive index for a cladding (114) than the refractive index of a core (112). In addition, the second segment has a larger core diameter and a smaller numerical aperture (NA) than the first segment. As a result of this excitation fiber, the excitation light that is propagated inside the first segment core is reliably incident inside the second segment core because the core diameter is larger in the second segment than the first segment. Of the excitation light incident inside the second segment core, the component having a greater propagation angle than the critical angle in the second segment is converted to a smaller propagation angle at the boundary between the core and the cladding, therefore said component has a sufficiently small propagation angle when emitted from the cladding in the emission end surface of the excitation fiber.</p> |
