A semiconductor laser diode includes multiple layers stacked along a first direction, in which the multiple layers include: a first multiple of semiconductor layers; an optical waveguide on the first multiple of semiconductor layers, in which the optical waveguide includes a semiconductor active region for generating laser light, and in which the optical waveguide defines a resonant cavity having an optical axis; and a second multiple of semiconductor layers on the optical waveguide region, in which a resistivity profile of at least one layer of the multiple layers varies gradually between a maximum resistivity and a minimum resistivity along a second direction extending orthogonal to the first direction, in which a distance between the maximum resistivity and the minimum resistivity is greater than at least about 2 microns.