| 摘要 |
Each of a first clad region (12) and a second clad region (13) has holes (12a, 13a) which have identical diameters and are periodically formed so that the first clad region (12) and the second clad region (13) each have an effective refractive index lower than a refractive index of a core region (11), the effective refractive index of the first clad region (12) being lower than that of the second clad region (13). |
