An ECLD assembly includes a thermally stabilized substrate, a laser device fixedly mounted in relation to the substrate, and a waveguide with a grating region having a grating formed therein. The waveguide is positioned to receive light emitted by the laser device and is attached to a top surface of the substrate. The ECLD's output wavelength is stabilized by one or more of the following: (1) mounting the waveguide so that its outer surface is less than 60 m, and preferably less than about 30 m from the top surface of the substrate; (2) placing a thermal cover (e.g., a generally semi-cylindrical shell or a strip of material formed with a V-groove) in thermal contact with the substrate and overlies at least a portion of the grating region; (3) bonding the waveguide to the substrate at first, second, and third positions where the first position is proximate the laser device, the second position is proximate a first end of the grating region, and the third position is proximate a second end of the grating region.