Single-mode DBR laser with improved phase-shift section

An edge-emitting laser for generating single-longitudinal mode laser light at a lasing wavelength, the laser comprising:

• a semiconductor active region for amplifying, by stimulated emission, light in the laser cavity at the lasing wavelength;
• a first grating section adjacent to the active region and having a first reflectance and a first effective index of refraction;
• a second grating section adjacent to the active region and having a second reflectance and the first effective index of refraction, the first and second grating sections having a Bragg wavelength substantially equal to the lasing wavelength;
• and
• a gratingless phase-shift section disposed adjacent to the active region and between the first and second grating sections and having a second index of refraction greater than the first effective index of refraction, wherein the phase-shift section has a length sufficient to impart a phase shift for light at the lasing wavelength sufficient to achieve single-longitudinal mode operation.