Patent ID: 7457339

Claim:
A semiconductor laser apparatus comprising: first and second semiconductor lasers; first and second optical waveguides connected to outputs of said first and second semiconductor lasers, respectively; a multiplexer for multiplexing outputs of said first and second optical waveguides; and a semiconductor optical amplifier adapted to receive output light from said multiplexer; wherein said first semiconductor laser and respective core layers of said first optical waveguide and said multiplexer are optically connected to one another, and said second semiconductor laser and respective core layers of said second optical waveguide and said multiplexer are optically connected to one another; wherein a first gate region is disposed between a MMI coupler (a) and a refractive index control core layer (b) in a front DBR region; and wherein assuming that a band-gap value of the core layer of said semiconductor amplifier is E SOA , an energy value of first signal light of said first semiconductor laser is E SIG1 , and a band-gap value of the core layer of said first region is E 1 , a relation of E SOA >E 1 is established so that the first core layer in said first region absorbs light from said semiconductor amplifier, and a relation of E SIG1 >E 1 is established and a current is applied to said first region so that said first core layer amplifies the first signal light.