An optical semiconductor device outputting a predetermined wavelength of laser light includes a quantum well active layer positioned between a p-type cladding layer and an n-type cladding layer in thickness direction. The optical semiconductor device includes a separate confinement heterostructure layer positioned between the quantum well active layer and the n-type cladding layer. The optical semiconductor device further includes an electric-field-distribution-control layer positioned between the separate confinement heterostructure layer and the n-type cladding layer and configured by at least two semiconductor layers having band gap energy greater than band gap energy of a barrier layer constituting the quantum well active layer. The optical semiconductor device is applied to a ridge-stripe type laser.

An optical semiconductor device outputting a predetermined wavelength of laser light includes a quantum well active layer positioned between a p-type cladding layer and an n-type cladding layer in thickness direction. The optical semiconductor device includes a separate confinement heterostructure layer positioned between the quantum well active layer and the n-type cladding layer. The optical semiconductor device further includes an electric-field-distribution-control layer positioned between the separate confinement heterostructure layer and the n-type cladding layer and configured by at least two semiconductor layers having band gap energy greater than band gap energy of a barrier layer constituting the quantum well active layer. The optical semiconductor device is applied to a ridge-stripe type laser.

A semiconductor laser element includes: a semiconductor substrate; a semiconductor laminate; a first electrode in which a ridge portion of the semiconductor laminate is embedded; and a second electrode. A first region of a side surface of the first electrode is separated from a first end surface in such a manner to extend away from the first end surface as the first region extends away from the ridge portion to both sides. A shortest distance between a first side surface and the first region is smaller than each of a shortest distance between a third side surface and a third region and a shortest distance between a fourth side surface and a fourth region. The first region does not include a corner in a range satisfying D.sub.1S.sub.1 and D.sub.1S.sub.2.

Provided is a semiconductor laser including: a semiconductor substrate; a semiconductor lamination portion laminated on a surface of the semiconductor substrate; and a first electrode and a second electrode. The semiconductor lamination portion includes an active layer, a first cladding layer located on the semiconductor substrate side with respect to the active layer, and a second cladding layer located on a side opposite to the semiconductor substrate with respect to the active layer, each of the first cladding layer and the second cladding layer includes an n-type cladding layer, one cladding layer of the first cladding layer and the second cladding layer further includes a p-type cladding layer located between the n-type cladding layer and the active layer.

A method of fabricating a semiconductor optical device is provided. The method includes steps of: providing a semiconductor substrate having a first conductivity type; depositing a first cladding layer having the first conductivity type on the semiconductor substrate; depositing an active layer on the first cladding layer; depositing a second cladding layer having a second conductivity type on the active layer, wherein the second conductivity type is different from the first conductivity type; forming a patterned mask layer over the second cladding layer; and performing an etching operation to sequentially remove portions of the second cladding layer, the active layer and the first cladding layer exposed through the patterned mask layer, thereby forming a mesa structure on the semiconductor substrate, wherein the etching operation uses an etchant comprising Br-based chemicals.

The present application is provided with: a ridge laminated with a first conductivity type cladding layer, an active layer, and a second conductivity type first cladding layer in order and having a top portion formed to be flat; a first buried layer buried on both side areas of the ridge; a second buried layer covering the first buried layer and protruding toward the center of the ridge and toward a top portion of the ridge to form an opening formed by protruding portions facing each other; and a second conductivity type second cladding layer buried on the second buried layer and in the opening, wherein a surface of the second buried layer on a side to the top portion of the ridge is formed so as to fit within a surface of the second conductivity type first cladding layer.