Patent ID: 7127145

Claim:
A semiconductor optical amplifier comprising: a first optical waveguide which propagates an input optical signal; an optical amplification section for carrying out amplification by causing induction discharge to occur with a resonator structure formed from a direction that, in a plane parallel to the first optical waveguide, intersects the optical propagation direction of the first optical waveguide, the optical amplification section amplifying the optical signal by causing stimulated emission with radiation incident on the first optical waveguide from a direction which is included in a plane parallel to the first optical waveguide and intersects an optical propagating direction of the first optical waveguide, and a cavity structure formed in a direction which intersects the optical propagating direction of the first optical waveguide, wherein, without injecting current into the first optical waveguide which propagates the input optical signal, the optical signal is amplified by causing stimulated emission by optically pumping carriers in the first optical waveguide with radiation incident on the first optical waveguide from a direction which is included in a plane parallel to the first optical waveguide and intersects the optical propagating direction of the first optical waveguide.