One embodiment of the present invention may include an edge emitting laser laterally grown on a semiconductor structure over a substrate as shown in FIGS. 1A and 1B. FIG. 1A is a schematic cross-sectional diagram representing the laterally grown edge emitting laser on the substrate, and FIG. 1B is a schematic top-view diagram representing the laterally grown edge emitting laser on the substrate according to an exemplary embodiment of the present invention. In FIG. 1B, the layers under the dielectric layer are shown for the purpose of providing better understanding of the structure of the edge emitting laser. Referring to FIGS. 1A and 1B, the edge emitting laser may include: a substrate 100; a first dielectric layer 401 disposed on the substrate 100; a semiconductor structure 301 disposed on the substrate 100 at a first direction, X direction, extending in a second direction, Y direction, and protruding from the substrate 100 through the first dielectric layer 401 in a third direction, Z direction, perpendicular to the first and second directions; a hard mask layer 200 disposed on top of the semiconductor structure 301; a first, a second and a third III-V optical layers 501, 502 and 503 sequentially and laterally grown on and from a sidewall of the semiconductor structure 301, and extending in the second direction; a cladding semiconductor layer 302 disposed on the substrate 100 next to the third III-V optical layer 503 and electrically connected to the III-V optical layer 503; a second dielectric layer 402 disposed on the substrate 100 to cover the first dielectric layer 401, the hard mask layer 200, the semiconductor structure 301, the cladding semiconductor layer 302, and the first, second and third III-V optical layers 501, 502 and 503; a first contact structure 601 and a second contact structure 602 disposed on and electrically connected to the semiconductor structure 301 and the cladding semiconductor layer 302, respectively.