Semiconductor laser element

A semiconductor laser element comprising:

• a first semiconductor layer of one conductivity type;
• a second semiconductor layer of the other conductivity type having a ridge extending along a laser output direction of said laser element, said ridge having a central portion, two peripheral portions sandwiching said central portion, and two transitional portions, each transitional portion provided between said central portion and a corresponding peripheral portion, and said central portion, said two peripheral portions, and said two transitional portions being arranged sequentially along said laser output direction;
• an active layer provided between said first semiconductor layer and said second semiconductor layer;
• window regions that are non-gain regions and are located in corresponding peripheral portions;
• and
• buried layers on both sides of said ridge except for window portions,
• wherein a difference in an equivalent refractive index between said central portion of the ridge and said peripheral portions on both sides is larger than a difference in an equivalent refractive index between said central portion of said ridge and transitional portions on both sides of said central portion in a gain region.