Semiconductor optical element, semiconductor optical integrated element, and method for manufacturing semiconductor optical element

A method of manufacturing a semiconductor optical element including a first cladding layer, a second cladding layer having a ridge formed in a ridge shape, an optical confinement layer interposed between the first cladding layer and the second cladding layer and adapted to propagate light, wherein the ridge is configured with a ridge bottom layer, a ridge intermediate layer, and a ridge top layer in this order from the optical confinement layer, ridge intermediate layer is formed wider in cross section perpendicular to an optical axis, which is a light propagating direction in the optical confinement layer, than the ridge bottom layer and the ridge top layer, and a thickness of the ridge bottom layer is in a range of 10% to 15% of a thickness of the ridge, the method comprising:

• growing a material for the optical confinement layer to form a first semiconductor layer on one surface of a semiconductor substrate serving as the first cladding layer, growing a material for the ridge bottom layer to form a second semiconductor layer, and then growing a material for the ridge intermediate layer to form a third semiconductor layer, growing a material for the ridge top layer to form a fourth semiconductor layer in this order from the semiconductor substrate;
• etching the fourth semiconductor layer to form the ridge top layer;
• and
• after etching the fourth semiconductor layer, etching the third semiconductor layer to have a width of the ridge intermediate layer, and
• after etching the third semiconductor layer, etching the second semiconductor layer to have a width of the ridge bottom layer.