Abstract: A buffer layer composed of an n-type semiconductor layer, a cladding layer composed of an n-type semiconductor layer, and an active layer are formed sequentially on an n-type semiconductor substrate. On the active layer, there are formed a first optical guiding layer composed of a p-type semiconductor layer including a loss varying layer composed of a p-type semiconductor layer having a bandgap smaller than that of the active layer and a second optical guiding layer composed of a p-type semiconductor layer in this order. On the second optical guiding layer, there is formed a third optical guiding layer composed of a p-type semiconductor layer extending in a stripe. On both sides of the third optical guiding layer on the second optical guiding layer, there are formed current blocking layers which become transparent to a lasing light generated in the active layer composed of the n-type semiconductor layer.