Patent ID: 8917753

Claim:
A method for aligning a semiconductor optical amplifier configured to optically amplify laser light from a laser light source and output the optically amplified laser light, the method comprising: adjusting a relative position of the semiconductor optical amplifier with respect to the laser light entering into the semiconductor optical amplifier by applying a given value of current to the semiconductor optical amplifier while the laser light from the laser light source enters the semiconductor optical amplifier so that a voltage applied to the semiconductor optical amplifier is at a maximum, wherein, the semiconductor optical amplifier includes a first electrode and a second electrode, the second electrode includes a first section and a second section, 0.001≦LAmp-2/LAmp-1≦0.01 is satisfied, where a length of the first section is LAmp-1 and a length of the second section is LAmp-2, light amplification is performed by applying voltage to the first section of the second electrode, and measurement for position adjustment is performed by applying voltage to the second section of the second electrode.