| 摘要 |
A high-order polarization conversion element is provided with: a substrate; a lower clad; a core (2) composed of an upper core (3) and a lower core (4) both having sectional rectangular shapes and given heights and formed from the same material; and an upper clad formed from the same material as the lower clad. In each of a start part (8) and an end part (9) of the core, the width of the lower core and the width of the upper core are the same, from the start part toward the end part, the width of the upper core and/or the width of the lower core continuously decreases, and neither the width of the upper core nor the width of the lower core increases, in the start part, the effective refractive index of TE1 is larger than the effective refractive index of TM0, in the end part, the effective refractive index of TM0 is larger than the effective refractive index of TE1, and in a part other than the start part and the end part between the start part and the end part, the core has a vertically asymmetrical structure in which the width of the upper core and the width of the lower core are different, and high-order polarization conversion is performed between TE1 of the start part and TM0 of the end part. |
