Semiconductor optical devices and methods of fabricating the same

A method of fabricating a semiconductor optical device, comprising:

• forming a light modulation core layer on a semiconductor substrate including a first mode converting region, a light amplification region, a second mode converting region, and a light modulating region;
• selectively removing the light modulation core layer to form a first removed region and a first residual pattern, the first residual pattern formed in a portion of the light modulating region and a portion of the second mode converting region;
• forming a first semiconductor layer in the first removed region;
• selectively removing the first semiconductor layer and the first residual pattern to form a second removed region, a first semiconductor pattern in the light amplification region, and a second residual pattern in the light modulating region;
• forming a second semiconductor layer in the second removed region, the second semiconductor layer being in contact with sidewalls of the first semiconductor pattern and sidewalls of the second residual pattern;
• and
• pattering at least the second semiconductor layer in the first mode converting region and the first semiconductor pattern in the light amplification region to form a first mode converting core and a light amplification core,
• wherein an energy band gap of the first semiconductor layer is different from an energy band gap of the second semiconductor layer.