A hybrid optical source that provides an optical signal having a wavelength (or a narrow band of wavelengths) is described. This hybrid optical source includes an optical amplifier (such as a III-V semiconductor optical amplifier) that is butt-coupled or vertically coupled to a silicon-on-insulator (SOI) platform, and which outputs an optical signal. The SOI platform includes an optical waveguide that conveys the optical signal. A temperature-compensation element included in the optical waveguide compensates for temperature dependence of the indexes of refraction of the optical amplifier and the optical waveguide. In addition, a reflector, adjacent to the optical waveguide after the temperature-compensation element, reflects a portion of the optical signal and transmits another portion of the optical signal that has the wavelength.