a semiconductor optical device having a quantum well structure which can easily integrate plural optical devices of band gaps which are different from each other , and yet can achieve a high coupling coefficient by means of disordering the quantum well structure to form a waveguide region except for the portion which is used as an active region . non - absorbing edges can be formed on the semiconductor laser on the optically integrated circuits by disordering the facets of the quantum well structure with ion implantation and thermal processing .