| abstract |
A light source includes a waveguide having an optical path that extends longitudinally between a back facet and an emission facet. The optical path includes a gain region that generates light through spontaneous emission. At least some of the spontaneous emission light propagates to a multiwavelength grating in the optical path. The multiwavelength grating has a relatively high reflectivity at a plurality of discrete wavelengths, and a relatively low reflectivity at wavelengths other than the discrete wavelengths. The spontaneous emission light at the discrete wavelengths reflects back to the gain region, is amplified by the gain region, and exits the waveguide through the emission facet to form the output light. The output light has relatively high intensity at the discrete wavelengths, and relatively low intensity away from the discrete wavelengths. A heating element can tune the multiwavelength grating, which can shift the discrete wavelengths, together, upward and downward. |