Patent ID: 8121169

Claim:
A method of controlling a DBR laser diode comprising an active region and a passive region aligned along an optical axis of the laser diode, wherein: the active region of the laser diode comprises an optical gain medium; the passive region of the laser diode comprises a DBR section; the DBR section comprises a Bragg grating tailored to contribute to selection of a laser emission wavelength from a range of available potential lasing modes; a waveguide portion of the passive region is tailored to be optically passive at the selected emission wavelength; the Bragg grating extends along the DBR section and comprises front and rear grating portions; the front grating portion of the DBR section is closer to the active region of the laser diode than is the rear grating portion of the DBR section, such that the contribution of the front grating portion to the reflectivity of the DBR section at the range of available potential lasing modes exceeds the contribution of the rear grating portion to the reflectivity of the DBR section at the range of available potential lasing modes and lasing mode selection in the laser diode is dominated by the front grating portion; the DBR section comprises a front heating element thermally coupled to the front grating portion of the DBR section and a rear heating element thermally coupled to the rear grating portion of the DBR section; the front and rear heating elements comprise portions of a single continuous electrically resistive heating element delineated by distinct heating element control nodes comprising a front control node, a rear control node, and a common control node positioned along the single heating element between the front and rear control nodes; the front and rear heating elements of the DBR section are arranged along distinct waveguide portions of the DBR section; the structure of the single continuous electrically resistive heating element is such that electrical current may flow between the three control nodes across the front and rear heating elements without disruption of electrical continuity along the single heating element to establish a thermal gradient along the waveguide portions in the DBR section to reduce refractive index non-uniformities along the waveguide portions in the DBR section; and the front heating element is controlled independently of the rear heating element to tune the selected emission wavelength and narrow the spectral bandwidth of the reflection spectra of the DBR section.