Semiconductor laser

A semiconductor laser comprising:

• a first clad layer having one of p-type conductivity and n-type conductivity,
• a first optical waveguide layer,
• a first barrier layer of GaAs1-y2Py2(0≦y2≦1),
• a quantum-well active layer of Inx3Ga1-x3As1-y3Py3(0≦x 3≦1, 0≦y3≦1),
• a second barrier layer of GaAs1-y2Py2(0≦y2≦1),
• a second optical waveguide layer, and
• a second clad layer having the of p-type conductivity and n-type conductivity formed in this order on a GaAs substrate,
• wherein each of the first and second clad layers is of a composition which matches with the GaAs substrate in lattice,
• wherein each of the first and second optical waveguide layers is of a InGaAsP composition which matches with the GaAs substrate in lattice, p1 wherein each of the first and second barrier layers is 10 to 30 nm in thickness and is of a composition which has tensile strain to the GaAs substrate,
• wherein the product of the tensile strain and the thickness of each of the first and second barrier layers being 5 to 20% nm,
• wherein the quantum-well active layer of In1-x3Ga1-x3As1-y3Py3 is 6 to 10 nm in thickness and is of composition which has compressive strain of not smaller than 1.0% relative to the GaAs substrate can realize oscillation at 950 to 1100 nm, and
• wherein a sum of a product of the tensile strain and the thickness of the first barrier layer and that of the second barrier layer is larger than a product of the compressive strain and the thickness of the quantum-well active layer.