Oxide-confined laser diodes with an integrated spot-size converter

We report a new technique for the monolithic integration of a GaAs-based InGaAs-GaAs strained quantum-well laser and a spot-size converter (SSC) to improve the fiber coupling characteristics. The selective wet oxidation of AlGaAs is used to simplify the fabrication scheme of the component to a single planar epitaxial growth step and one conventional noncritical etch. This approach also allows us to avoid the photolithography of narrow features. An excellent reproducibility of the fabrication scheme was found. The integrated SSC exhibits very low transformation losses and a low beam divergence of 7.5°×13.5°. The coupling efficiency to a 980-nm single-mode fiber is improved from -6.34 dB for a reference laser to -1.49 dB for the tapered device. The -1-dB alignment tolerance is ±1.5 μm in the transverse direction and ±1.6 μm in the lateral direction, respectively.