Patent ID: 8705901
Filing Date: 2014-04-22
Classification: G02B

Abstract:
1. A method for making a polarization rotator, comprising the steps of: forming a structure including a semiconductor substrate and a mesa part, the semiconductor substrate having a main surface, the mesa part extending in a first direction parallel to the main surface of the semiconductor substrate; forming a first semiconductor layer on the main surface of the semiconductor substrate and on a side face of the mesa part, the first semiconductor layer having a mesa-part-adjacent portion in contact with the side face of the mesa part, at least part of the mesa-part-adjacent portion having an inclined surface; forming a second semiconductor layer on the first semiconductor layer, the second semiconductor layer having an inclined portion located on the inclined surface of the mesa-part-adjacent portion; forming a semiconductor laminate by forming a third semiconductor layer on the second semiconductor layer, the semiconductor laminate including the first semiconductor layer, the second semiconductor layer, and the third semiconductor layer; forming a mask layer on a surface of the third semiconductor layer, the mask layer extending in the first direction; forming a stripe-shaped mesa by etching the semiconductor laminate using the mask layer, the stripe-shaped mesa including a first semiconductor core constituted by at least part of the inclined portion of the second semiconductor layer; and forming a first semiconductor cladding by forming a fourth semiconductor layer on a side face of the stripe-shaped mesa, the first semiconductor cladding surrounding the first semiconductor core, wherein the first semiconductor core and the first semiconductor cladding form a polarization rotating unit of the polarization rotator; the inclined surface of the mesa-part-adjacent portion extends in a second direction that forms an acute angle with the main surface of the semiconductor substrate; and in a cross section perpendicular to the first direction, the inclined portion of the second semiconductor layer extends in the second direction.