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Fabrication and characterization of a spot-size converter-integrated 1.3 µm FP laser diode

We fabricated a spot-size converter-integrated 1.3 µm laser diode with a conventional buried-heterostructure laser process. For the spot-size converter, we employed a double-waveguide structure in which a ridge-based passive waveguide was incorporated. The passive waveguide was optically combined with a laterally tapered active waveguide to control the mode size. The device showed a low threshold current of 6.5 mA and high slope efficiency of 0.29 W A−1. The beam divergences in horizontal and vertical directions were 6.1° and 15.7°, respectively. A minimum coupling loss was 3.7 dB and the alignment tolerance with the additional 1 dB loss was ±2.4 µm for horizontal and ±1.7 µm for vertical directions. The 3 dB modulation bandwidth was 4.8–6.8 GHz with the operation current between 40 mA and 100 mA. We obtained clear open eye patterns at 1.25 Gbps operation.