Index and gain coupled distributed feedback laser

A method, comprising:

• injecting current into epitaxial layers of a laser, the epitaxial layers including an active region surrounded by first and second waveguide layers, the active region extending along a light-propagation direction of the laser;
• modulating a current flow into the active region via two or more mask openings formed within a dielectric layer on a surface parallel to the active region, the mask openings extending normal to the light-propagation direction and spaced apart in the light-propagation direction of the laser;
• and
• modulating a real part of an effective refractive index of the laser via a refractive grating formed on the dielectric mask openings, the refractive grating comprising three-dimension grating features spaced apart in the light-propagation direction of the laser.

A method of forming a laser, comprising:

• forming, on a substrate, a first epitaxial part of the laser comprising at least an active region layer surrounded by first and second waveguide layers;
• forming a dielectric layer over the first epitaxial part;
• patterning two or more mask openings within the dielectric layer, the mask openings extend normal to a light-propagation direction of the laser and are spaced apart in the light-propagation direction of the laser;
• and
• forming, in the mask openings using selective area epitaxy, a second epitaxial part of the laser comprising a refractive grating comprising three-dimensional grating features.