What is claimed is:1. An edge emitting laser comprising:a substrate;a first dielectric layer disposed on the substrate;a semiconductor structure on the substrate at a first direction, extending in a second direction, and protruding from the substrate through the first dielectric layer in a third direction, perpendicular to the first and second directions;a hard mask layer disposed on top of the semiconductor structure;a first, a second and a third III-V optical layers sequentially and laterally grown on and from a sidewall of the semiconductor structure, and extending in the second direction;a cladding semiconductor layer disposed on the substrate next to the third III-V optical layer and electrically connected to the third III-V optical layer;a second dielectric layer disposed on the substrate to cover the first dielectric layer, the hard mask layer, the semiconductor structure, the cladding semiconductor layer, and the first, second and third III-V optical layers; anda first contact structure and a second contact structure disposed on and electrically connected to the semiconductor structure and the cladding semiconductor layer, respectively.2. The edge emitting laser of claim 1, wherein each of the first, second and third III-V optical layers independently comprises a III-V semiconductor including at least one of group III elements of boron (B), gallium (Ga), aluminum (Al) and indium (In), and at least one of group V elements of nitrogen (N), phosphorus (P), arsenic (As), antimony (Sb) and bismuth (Bi).3. The edge emitting laser of claim 1, wherein the semiconductor structure comprises an n-doped semiconductor, the cladding semiconductor layer comprises a p-doped semiconductor, the first III-V optical layer comprises an n-doped III-V semiconductor, and the third III-V optical layer comprises a p-doped III-V semiconductor.4. The edge emitting laser of claim 3, wherein the semiconductor structure comprises an n-doped silicon, the cladding semiconductor layer comprises a p-doped silicon, the first III-V optical layer comprises an n-doped AlGaAs, and the third III-V optical layer comprises a p-doped AlGaAs.5. The edge emitting laser of claim 1, wherein the second III-V optical layer comprises a quantum well structure or multiple quantum well structures.6. The edge emitting laser of claim 1, wherein the second III-V optical layer comprises InGaAs.7. The edge emitting laser of claim 1, wherein the first dielectric layer and the second dielectric layer comprise silicon oxide.8. The edge emitting laser of claim 1, wherein a width of the semiconductor structure in the first direction is about 0.5 μm to about 2 and a length of the semiconductor structure in the second direction is about 100 μm to about 8000 μm.9. The edge emitting laser of claim 1, wherein a width in the first direction for the first III-V optical layer is about 20 nm to about 50 nm, for the second III-V optical layer is about 5 nm to about 10 nm, and for the third III-V optical layer is about 20 nm to about 50 nm.10. The edge emitting laser of claim 1, wherein a width of the cladding semiconductor layer in the first direction is about 0.5 μm to about 2 and a length of the cladding semiconductor layer in the second direction is about 100 μm to about 8000 μM.11. An edge emitting laser comprising:a semiconductor structure disposed on a substrate;a first, a second and a third III-V optical layers sequentially and laterally grown on and from a sidewall of the semiconductor structure;a cladding semiconductor layer disposed next to the third III-V optical layer and electrically connected to the third III-V optical layer; anda first contact structure and a second contact structure disposed on and electrically connected to the semiconductor structure and the cladding semiconductor layer, respectively,wherein each of the first, second and third III-V optical layers independently comprises a III-V semiconductor including at least one of group III elements of boron (B), gallium (Ga), aluminum (Al) and indium (In), and at least one of group V elements of nitrogen (N), phosphorus (P), arsenic (As), antimony (Sb) and bismuth (Bi).12. The edge emitting laser of claim 11, wherein the semiconductor structure comprises an n-doped silicon, the cladding semiconductor layer comprises a p-doped silicon, the first III-V optical layer comprises an n-doped AlGaAs, the second III-V optical layer comprises InGaAs, the third III-V optical layer comprises a p-doped AlGaAs, and the first III-V optical layer is laterally grown on and from Si (111) crystal plane of the sidewall of the semiconductor structure.