A light source emits first incident light to a first polarization-reversed structure. The first polarization-reversed structure then converts the wavelength of the first incident light to emit a higher harmonic wave. A fiber coupler divides the higher harmonic wave output from the first polarization-reversed structure into output light emitted from the light source device and feedback light. The feedback light enters a second polarization-reversed structure. The second polarization-reversed structure then converts the wavelength of the feedback light to emit second incident light. The second incident light has the same wavelength as the first incident light. The second incident light enters a first wavelength converter.