We report the design, fabrication, and characterization of 1310-nm-emission buried-heterostructure (BH) spot-size-converter (SSC)-integrated distributed-feedback (DFB) laser diode (LD) with record power efficiency of 20% at optical power of more than 100 mW at 75°C and current of 400 mA. The SSC also functions as semiconductor optical amplifier so that with laser oscillation takes place in the DFB section, the SSC provides optical gain while shaping the optical mode to give a lowest possible far-field (FF) of 9 ° ( h ) × 14.5 ° ( v ) . The measured coupling loss of the SSC-integrated DFB LD output to 10 μm-radius-of-curvature lensed single-mode-fiber is ∼0.9 dB. For Co-Package Optics application, the SSC-integrated DFB LD is a potentially viable candidate for External-Laser-Source module, or for hybrid-integrated laser-source on silicon photonics (SiPh) platform via flip-chip and butt-coupling of light to SiPh waveguide.