Patent ID: 8073029

Claim:
A semiconductor optical device of an edge-emitting type having a predetermined emission wavelength, the semiconductor optical device consisting essentially of: a semiconductor substrate; a single DBR layer having first and second semiconductor layers stacked alternately and provided on the semiconductor substrate; a first cladding layer having a thickness of at least 1.5 Î¼m but not more than 2 Î¼m provided on the first semiconductor DBR layer; an active layer, with upper and lower optical confinement layers, provided on the first cladding layer; a second cladding layer provided on the active layer; a ridge structure extending in a light propagation direction; a front facet and a back facet; a laser cavity defined only by the front facet and the back facet in the light propagation direction; and wherein the semiconductor substrate has a bandgap higher than that of the active layer; and wherein the first semiconductor DBR layer is transparent to the emission wavelength, and the first and second semiconductor layers have respective refractive indices different from each other, thereby avoiding substrate-mode excitation.