Semiconductor laser device with window regions

A semiconductor laser device with window regions, in which a double hetero structure including cladding layers and an active layer sandwiched by the cladding layers is formed on a semiconductor substrate, the double hetero structure is buried in burying layers with a bandgap larger than that of the active layer, and the burying layers form window regions situated at both end facets of the double hetero structure, wherein the window regions have a waveguide structure including a plurality of semiconductor layers with different bandgaps, wherein the plurality of semiconductor layers in the window regions comprise a window region waveguide layer and window region cladding layers which are provided above and below the window region wave guide layer and which have a bandgap larger than that of the window region waveguide layer, and further wherein the window region waveguide layer is provided so that the position and size thereof correspond to those of the active layer, and a waveguide mode of the active layer and that of the window region waveguide layer match with each other.