A low-cost and low-power-consumption optical transmitter with a narrow shoreline is crucial for short-reach optical communication. To increase the shoreline bandwidth density (Gbps/mm) at low cost, multiple optical components, including lasers, should be integrated on a single chip. In this study, we develop a sixteen-channel membrane laser array integrated with silica-based spot-size convertors on a SiO2/Si substrate, with a footprint of 1.11 × 2.75 mm2. A thin (340 nm) membrane buried-heterostructure sandwiched between low-index silica-based materials provides high carrier and optical confinement, which contributes to reducing power consumption. We demonstrated direct modulation with 28- and 56-GBaud PAM4 signals and verified that 2-km data transmission is feasible for all sixteen channels.