Abstract: In a semiconductor laser device comprising a semiconductor laser main body having an active layer formed between a pair of cladding layers, and a non-absorbing layer of InGaP formed on the facets of the semiconductor laser main body and having a band gap greater than the band gap of the active layer,a diffusion blocking layer of, for example, Si, SiN or Ge is formed on the surface of the non-absorbing layer, and a di-electric protective layer of, for example, AlO.sub.x, SiO.sub.x, SiN.sub.x or MgO.sub.x for regulating reflectance at the facets and protecting the non-absorbing layer is formed on the diffusion blocking layer.

Abstract: A semiconductor laser device having a body with opposed facets and including an active region with aluminum diffused into the active region along the facets thereof. Adding aluminum to the portions of the active region along the facets increases the bandgap of the active region along the facets and provides a semiconductor laser device having an increased catastrophic optical damage (COD) level. The semiconductor laser device is produced by depositing a thin film of aluminum on the facets of the semiconductor laser device and then heat treating to cause diffusion of the aluminum film or phosphorus into the body of the semiconductor laser device along the facets thereof, thereby changing the composition of the semiconductor laser device body along the facets. Alternatively, phosphorus may be diffused into the body of the semiconductor laser device along the facets thereof.

Abstract: There is provided a semiconductor laser device capable of emitting a laser beam having stable transverse modes. A ridge type semiconductor laser device comprises an upper clad layer 15 left on its active layer to a thickness (d) between 0.25 and 0.50 m in order to ensure a stable production of fundamental transverse modes for laser operation and a rib-shaped clad layer 16 having a bottom width (W) between 2.0 .mu.m and 3.5 .mu.m and projecting from the upper clad layer in juxtaposition with the light emitting region of the active layer 13. When d and W are found within the respective ranges, the device emits a laser beam having stable transverse modes.