A grating-stabilized semiconductor laser comprises a semiconductor laser gain medium, an integrated low-index waveguide, and a waveguide grating segment providing optical feedback for laser oscillation. The laser may be adapted for multi-mode or single-mode operation. A multiple-mode laser may oscillate with reduced power and/or wavelength fluctuations associated with longitudinal mode wavelength shifts, relative to Fabry-Perot lasers lacking gratings. A single-mode laser may include a compensator, wavelength reference, and detector for generating an error signal, and a feedback mechanism for controlling the compensator for maintaining the laser wavelength locked to the reference. The laser may include means for altering, enhancing, tuning, and/or stabilizing the waveguide grating reflectivity spectral profile. The laser may be adapted for optical transverse-coupling to another waveguide.