Patent ID: 7627012

Claim:
A distributed feedback (DFB) semiconductor laser device, comprising: a laser cavity extending from a front facet to a rear facet and between first and second sides, the laser cavity including at least first and second main cavity sections and a wavelength monitoring section; an active region located in the laser cavity, the active region comprising a plurality of quantum-well layers and barrier layers between the quantum-well layers, the bandgap energy of the barrier layers being greater than the bandgap energy of the quantum-well layers; and a grating formed by grooves extending at least partially through the active region and spaced along at least a portion of the laser cavity, wherein the grating comprises first and second grating sections in the first and second main cavity sections, respectively, and a second-order grating section in the wavelength monitoring section of the cavity, wherein the second grating section is longer than the first grating section and provides a main feedback mechanism for lasing, wherein the first grating section is configured to reflect the lasing wavelength such that laser radiation is emitted from the front facet, and wherein the second-order grating section in the wavelength monitoring section is configured to emit laser radiation from the first side.