A laser includes an active region surrounded by first and second waveguide layers. Two or more mask openings are formed within a dielectric layer on a surface parallel to the active region. A refractive grating is formed on the dielectric mask openings and includes three-dimensional grating features spaced apart in the light-propagation direction of the laser. The refractive grating provides modulation of a real part of the effective refractive index of the laser and modulation of the imaginary part is provided by modulation of the current flow through the mask openings.