Semiconductor laser device and a method for driving the same

In a semiconductor laser device comprising a laser-oscillating optical waveguide composed of a control region which functions to absorb light and main regions which function to oscillate laser, said control region being positioned in the center portion of said optical waveguide and said main regions being positioned on both ends of said control region, and said laser device further comprises a shunting means by which

• the amount of current injected into each of said control region and said main regions is controlled in such a manner that when said laser devices achieve low output power operation, said current flowing to said control region is maintained at a low level whereby said control region becomes a saturable absorption region, and when said laser devices achieve high output power operation, said current flowing to said control region is maintained at a high level.