| 摘要 |
<p>PROBLEM TO BE SOLVED: To provide a polarization rotation circuit that does not incur a rise in manufacturing time and an increase in the complexity of a manufacturing device by limiting the formation of a silicon nitride layer.SOLUTION: The polarization rotation circuit comprises tapered waveguides 102, 103 and 104 whose width gradually expands, and an asymmetric directional coupler having a wide waveguide 105 and a narrow waveguide 106, one end of the wide waveguide 105 being optically connected to a wide end of the tapered waveguide 104. An upper clad layer made of a silicon nitride layer is provided in only an area 109 which is above the core of the tapered waveguide 103 assuming a polarization conversion function, and which, when a circuit configuration plane is looked at, overlaps the tapered waveguide 103 and includes the tapered waveguide 103. The silicon nitride layer is not provided in other mode conversion circuit and input/output waveguides 101, 107 and 108 than the tapered waveguide 103 assuming the polarization conversion function.</p> |
