A laser includes a substrate and a resonant cavity. In addition to an active gain region, a first phase shift region, an optical branching region, and N reflective mode selection regions, the resonant cavity further includes a highly reflective surface, where a reflectivity of the highly reflective surface is greater than reflectivities of the N reflective mode selection regions, so that laser beams are output from the N reflective mode selection regions. Because the laser naturally includes at least two reflective mode selection regions, at least two laser beams are output. According to the laser provided by the embodiments of the present invention, one laser can output two laser beams or even multiple laser beams; therefore, laser beam generation efficiency is high and average costs for generating a single laser beam are accordingly reduced.