A multi-layer composite heat dissipation substrate includes a substrate body, a first insulation layer, a first electrode layer, a second electrode layer, and a solder layer. The substrate body has a first surface and a second surface. The first insulating layer is formed on the first surface of the substrate body. The first insulating layer is made of an insulating material selected from the group consisting of: nitride, oxide, and oxynitride. The first electrode layer is formed on a top surface of the first insulating layer. The second electrode layer is located below the substrate body. The solder layer is formed on a top surface of the first electrode layer.

A cladding-less GaN-based thin-film edge-emitting laser is formed by: attaching a typical LED wafer to a substrate; removing its sapphire substrate to expose its n-GaN and the u-GaN buffer layers; thinning the film thickness to maximize the overlap factor; depositing another reflective metallic layer on the n-GaN surface for optical confinement and electrical contact; defining a pattern of the edge-emitting cavity by nanolithography techniques; and using an ICP etch to transfer the pattern to the thin film. In a second embodiment, the LED epitaxy structure is transformed into a laser diode by bonding it to a substrate with a Bragg reflector. After bonding and substrate removal, the bottom of the LED epitaxy is exposed for etching. In a third embodiment, a polariton edge-emitting laser is formed by utilizing Distributed Bragg Reflectors (DBRs) on both sides of the edge-emitting laser.

A device includes a first element having a passive waveguide structure supporting a first optical mode, a second element providing heat spreading functionality, a third element thermally coupled to the second element, having an active waveguide structure supporting a second optical mode, and a fourth element, at least partly butt-coupled to the third element, having an intermediate waveguide structure supporting intermediate optical modes. A tapered waveguide structure in either one of the first and fourth elements facilitates efficient adiabatic transformation between the first optical mode and one of the intermediate optical modes. No adiabatic transformation occurs between any of the intermediate optical modes and the second optical mode. Mutual alignments of the first, second, third and fourth elements are defined using lithographic alignment marks that facilitate precise alignment between layers formed during processing steps of fabricating the first, second, third and fourth elements.

A laser is provided, which includes a frame, a substrate, heat sinks, light-emitting chips, and protective devices. The frame and the heat sinks are fixed to the substrate. The heat sinks, the light-emitting chips, and the protective devices are located inside the frame. The light-emitting chips and the protective devices are fixed to the heat sinks, and the light-emitting chip and the corresponding protective device have a spacing therebetween in a length direction of the heat sink.