Semiconductor optical integrated device

A semiconductor optical integrated device in which a semiconductor optical amplifier and a semiconductor laser are monolithically integrated on a semiconductor substrate, the semiconductor optical integrated device comprising:

• a passive waveguide portion arranged between the semiconductor optical amplifier and the semiconductor laser;
• and
• a ground electrode arranged on a lower surface of the semiconductor substrate, wherein
• the semiconductor laser is a wavelength-tunable laser and includes first and second mirrors each having length, a gain portion, and a phase adjusting portion, the second mirror being arranged on a side closer to the semiconductor optical amplifier,
• the second mirror is a distributed bragg reflector made from semiconductor,
• the semiconductor optical amplifier includes a semiconductor optical amplifier electrode on a side opposite to a side in contact with the semiconductor substrate,
• the passive waveguide portion includes a passive waveguide electrode on a side opposite to a side in contact with the semiconductor substrate,
• the passive waveguide electrode is electrically connected to the ground electrode,
• the passive waveguide portion is arranged between the second mirror and the semiconductor optical amplifier,
• the semiconductor laser and the semiconductor optical amplifier are optically connected via the passive waveguide portion,
• the second mirror, the semiconductor optical amplifier, and the passive waveguide portion are faced with a common upper cladding layer on a side opposite to a side in contact with the semiconductor substrate,
• the first mirror and the gain portion have a buried structure in which a stripe mesa structure is buried on both sides with a current blocking structure constituted of a p-type InP buried layer and a n-type InP current blocking layer,
• the common upper cladding layer on the buried structure is a common upper cladding layer in the first mirror and the gain portion,
• the second mirror is configured to be variable in wavelength characteristics by changing a refractive index of an optical waveguide layer of the second mirror by heating with a heater provided with the second mirror, and
• a leakage current from the semiconductor optical amplifier flows through the passive waveguide portion.