Semiconductor laser

A semiconductor laser, comprising:

• a compressively strained quantum well semiconductor laser including GaInAs/GaInAsP and including p-type and n-type waveguide layers, each of said p-type and n-type waveguide layers including plural waveguide layers each with a different band gap;
• a first p-type carrier blocking layer provided in said p-type waveguide layer, wherein a value of a band gap of said first carrier blocking layer is larger than a smallest value of said different band gaps of said plural waveguide layers of said p-type waveguide layer;
• and
• a second n-type carrier blocking layer provided in said n-type waveguide layer, wherein a value of a band gap of said second carrier blocking layer is larger than a smallest value of said different band gaps of said plural waveguide layers of said n-type waveguide layer,
• wherein a difference between the band gap of each carrier blocking layer and the smallest value of the different band gaps of the respective waveguide layers is in the range of 85 meV-190 meV,
• wherein an energy difference between a band gap of a first ground state of the quantum well layers and the band gap of each of the carrier blocking layers is in the range of 300 meV-500 meV, and
• wherein a thickness of the carrier blocking layer is in the range of 5 nm-10 nm.