| 摘要 |
PROBLEM TO BE SOLVED: To provide a semiconductor optical amplifier (SOA) capable of optical amplification of polarization independence across a wide gain band in a wavelength range for performing optical communication.SOLUTION: A semiconductor optical amplifier comprises: an active layer 14 of a quantum well which has barrier layers 142 and composite quantum well layers 141 each composed of a plurality of semiconductor layers and in which the barrier layers 142 and the composite quantum well layers 141 are alternately stacked. The plurality of semiconductor layers of the composite quantum well layer 141 are composed of at least one layer of a quantum level control layer 143 for controlling a quantum level in the composite quantum well layer 141 and at least one layer of main quantum well layer 144 having bandgap smaller than that of the quantum level control layer 143. At least one layer of the quantum level control layer 143 and the main quantum well layer 144 has tensile strain against the substrate. |
