Provided is a laser device. In the laser device, an active layer is connected to a stem core of a 1×2 splitter on a substrate, a first diffraction grating is coupled to a first twig core of the 1×2 splitter, and a second diffraction grating is coupled to a second twig core of the 1×2 splitter. An active layer-micro heater is designed to supply heat to the active layer. First and second micro heaters are designed to supply heats to the first and second diffraction gratings, respectively, thereby varying a Bragg wavelength.