Apparatus comprise a semiconductor waveguide extending along a longitudinal axis and including a first waveguide section and a second waveguide section, wherein a lateral refractive index difference defining the semiconductor waveguide is larger for the first waveguide section than for the second waveguide section, and an output facet situated on the longitudinal axis of the semiconductor waveguide so as to emit a laser beam propagating in the semiconductor waveguide, wherein the first waveguide section is situated between the second waveguide section and the output facet and wherein the lateral refractive index difference suppresses emission of higher order transverse modes in the laser beam emitted by the output facet.