Performance heterogeneous lasers and active components

A device comprising:

• first, second and third element fabricated on a common substrate;
• wherein the first element comprises an active waveguide structure supporting a first fundamental optical mode and first higher-order optical mode, the second element comprises a passive waveguide structure supporting a second optical mode, and the third element, at least partly butt-coupled to the first element, comprises an intermediate waveguide structure supporting intermediate optical modes;
• wherein first element comprises at least three sublayers (401a, 401b, 401c) and a modal gain control structure;
• wherein one of the sublayers, the active region sublayer (401b), of the first element is positioned between two other sub-layers and comprises an active region comprising at least one of quantum wells and quantum dots;
• wherein the modal gain control structure including at least one of pad structures comprising metal or having bandgap below a photon energy of the modes in active waveguide structure is placed directly on top of the active region sublayer without a contact sublayer between the modal gain control structure and the active region sublayer;
• wherein an overlap between the first higher-order optical mode and at least one of the modal gain control structures is larger than the overlap between the first fundamental optical mode and the same modal gain control structure;
• wherein a tapered waveguide structure in at least one of the second and third elements facilitate efficient adiabatic transformation between the second optical mode and one of the intermediate optical modes;
• wherein no adiabatic transformation occurs between any of the intermediate optical modes and the first optical mode;
• and
• wherein mutual alignments of the first, the second and the third element are defined using lithographic alignment marks that facilitate precise alignment between layers formed during processing steps of fabricating the first, the second and the third element.