High-Performance 1.55-$\mu$ m Superluminescent Diode With Butt-Coupled Spot-Size Converter

We report the design and fabrication of a novel 1.55-$ \mu$m spot-size converter superluminescent diode (SLD) for optical access networks. The active section of SLD was fabricated by using a planar buried heterostructure to adopt the double- waveguide- core structure for low-threshold and high-output power operation at a low injection current. A ridge-based passive waveguide was employed for an efficient coupling to a planar lightwave circuit. The threshold current was as low as 14 mA, and the maximum output power was as high as 28 mW with ripple less than 3 dB at an injection current of 200 mA.