Semiconductor optical devices with differential grating structure and method for manufacturing the same

A semiconductor optical device comprising:

• a resonator having three regions consisting of reflective, optical gain, and phase control regions,
• wherein at least one region of the reflective and optical gain regions includes:
• an n-type InP substrate;
• a stack structure on the InP substrate including a waveguide and active layers;
• a first grating formed under the stack structure and on the InP substrate;
• and
• a second grating formed on the stack structure.

A method for manufacturing a semiconductor optical device comprising the acts of:

• forming a first grating on an n-type InP substrate;
• forming an n-type InP clad layer on the first grating;
• forming a waveguide layer on the n-type InP clad layer;
• forming an active layer on the waveguide layer;
• forming a p-type InP clad layer on the active layer;
• and
• forming a second grating on the p-type InP clad layer.