| 摘要 |
PROBLEM TO BE SOLVED: To provide a semiconductor optical amplifier for improving its gain while inhibiting the increase in noise, and to provide the manufacturing method of the semiconductor optical amplifier. SOLUTION: The semiconductor optical amplifier has a waveguide layer 12 having a plurality of active layers 24 that are formed on a substrate 10 while they are separated one another, and an absorption layer 34 formed among the plurality of active layers. A forward current (+I) is injected into a region where the active layers are formed, and a backward bias (-V) is applied to a region where the absorption layer is formed. In this state, the peak wavelength of natural emission light being amplified in the active layer becomes shorter than the wavelength of signal light inputted to the waveguide layer, and the wavelength of the absorption end of the absorption spectrum of the absorption layer becomes shorter than the wavelength of the signal light.
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