A multi-section semiconductor optical amplifier (SOA) includes at least two sections in series—an input section at an input side and an output section at an output side—with the input section having a higher optical confinement (also referred to as a high gamma) and the output section having a lower optical confinement (also referred to as a low gamma). The input section may also have a shorter length than the output section. The multi-section structure allows optimizing the input side and the output side design separately such that the input section provides a high gain section configured to quickly increase optical power and the output section provides a low differential gain section that improves saturation. As a result, the multi-section SOA can achieve higher output power with high gain and lower signal noise while demanding low input power.