Semiconductor optical element and semiconductor optical device comprising the same

A semiconductor optical device comprising:

• a semiconductor optical element configured to emit or absorb light, the semiconductor optical element comprising:
• a lower structure that includes a multiple quantum well layer;
• an upper mesa structure that is disposed on the lower structure;
• a current injection structure that is disposed on the upper mesa structure,
• when seen from an optical axis of the emitted or absorbed light, a width of a portion of the current injection structure in contact with the upper mesa structure is smaller than a width of the upper mesa structure,
• the portion of the current injection structure in contact with the upper mesa structure consisting of InP, and
• an average refractive index of the upper mesa structure is higher than a refractive index of the InP forming the current injection structure;
• and
• an insulating film covering both side surfaces of the upper mesa structure and a part of an upper surface of the upper mesa structure;
• and
• a semiconductor laser integrated with the semiconductor optical element.