Semiconductor laser device in which compressive strain active layer is sandwiched between tensile strain optical waveguide layers and average strain is limited

A semiconductor laser device comprising:

• a substrate;
• and
• an active region being formed above said substrate and including,
• an active layer having a plurality of quantum well sublayers and at least one barrier sublayer formed between said plurality of quantum well sublayers, and
• optical waveguide layers having a predetermined amount of tensile strain and a first predetermined total thickness and being formed so that said active layer is sandwiched between the optical waveguide layers;
• wherein said plurality of quantum well sublayers have a predetermined amount of compressive strain and a second predetermined total thickness, said at least one barrier sublayer has said predetermined amount of tensile strain and a third predetermined total thickness, and an absolute value of a sum of first and second products is equal to or smaller than 0.05 nm, where said first product is a product of said predetermined amount of compressive strain and said second predetermined total thickness, and said second product is a product of said predetermined amount of tensile strain and a sum of said first predetermined total thickness and said third predetermined total thickness.