A groove large-optical cavity (G-LOC) InGaAsP/InP laser has been fabricated on semi-insulating InP substrate. The fabrication process involves only a single step liquid phase epitaxial growth on a channeled substraote, and is thus simple and reproducible. The device combines the advantages of the groove laser and the LOC structure. In groove laser, the presence of a built-in real index waveguide makes it possible to obtain low-threshold, single mode operation, while the LOC structure posseseg the potential capability of delivering Jiigh output power. As a result, threshold current as low as 25 mA and an output power of 200 mW per facet have been achieved. The G-LOO Laser can be used as light source in applications such as optical oom-xuunication and Signal process, as well as integrated with, other optoelectronic devices.