The first, second and third III-V optical layers 501, 502 and 503 may be sequentially and laterally grown on and from a sidewall of the semiconductor structure 301, and may extend in the second direction, Y direction. Each of the first, second and third III-V optical layers 501, 502 and 503 may independently include a III-V semiconductor which includes 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). For example, the III-V semiconductor may be a binary, ternary, or quaternary alloy including at least one of group III elements and at least one of group V elements. The binary alloy may be, for example, one of GaAs, GAN, GaP, InP, InAs, InSb, and GaSb. The ternary alloy may be, for example, one of AlGaAs, InGaAs, InGaP, InGaSb, GaAsSb, AlInAs, AlInSb, AlGaP, InAsSb, GaAsP, InGaN, and AlGaN. The quaternary alloy may be, for example one of InGaAlP, AlGaAsSb, AlGaPSb, InGaAlSb, and AlGaPAs. The first III-V optical layer 501 may include an n-doped III-V semiconductor, and the third III-V optical layer 503 may include a p-doped III-V semiconductor. For example, the first III-V optical layer 501 may include an n-doped AlGaAs, and the third III-V optical layer 503 may include a p-doped AlGaAs. They may be heavily doped, for example, the first III-V optical layer 501 may include an AlGaAs n+, and the third III-V optical layer 503 may include a AlGaAs p+. The first III-V optical layer 501 is laterally grown from the sidewall of the semiconductor structure 301 and is directly connected to the semiconductor structure 301. The second III-V optical layer 502 may be laterally grown on the sidewall of the first III-V optical layer 501. The third III-V optical layer 503 may be laterally grown on the sidewall of the second III-V optical layer 502, with the second III-V optical layer 502 interposed between the first III-V optical layer 501 and the third III-V optical layer 503. When the second III-V optical layer 502 containing a material having a smaller bandgap energy is interposed between the first and third III-V optical layers 501 and 503 containing materials having higher energy gaps, a double heterojunction is formed. A double heterojunction consists of two heterojunctions, and the recombination of carriers is restricted to the low bandgap region, for example, in the second III-V optical layer 502. The low bandgap region may be called active region, and the second III-V optical layer 502 may include GaAs. In addition, the second III-V optical layer 502 may include a thin quantum well structure or multiple quantum well structures. The second III-V optical layer may include InGaAs. A width in the first direction, X direction, for the first III-V optical layer 501 may be from about 20 nm to about 50 nm, for the second III-V optical layer 502 may be from about 5 nm to about 10 nm, and for the third III-V optical layer 503 may be from about 20 nm to about 50 nm. In an exemplary embodiment of the present invention, at least one of the first, second and third III-V optical layers 501, 502 and 503 may include a multilayer structure. For example, the second III-V optical layer 502 including InGaAs quantum well structure may be centered between two layers of graded-index separate confinement AlGaAs heterostructure (n-graded AlGaAs layer and p-graded AlGasAs layer on each side) to serve as the high refractive index core of the optical waveguide. The low refractive index cladding layers of AlGaAs n+ layer and AlGaAs p+ layer may be deposited on both n and p sides to provide a symmetric positive refractive index waveguide.