Small-Pitch Flip-Chip-Bonded VCSEL Arrays Enabling Transmitter Redundancy and Monitoring in 2-D 10-Gbit/s Space-Parallel Fiber Transmission

We demonstrate novel pixel architectures in 2-D vertical-cavity surface-emitting laser (VCSEL) arrays offering additional functionality without sacrificing efficient fabrication, compactness, and low module cost. Very high flip chip VCSEL packing densities enable both a built-in 3-per-channel VCSEL redundancy as well as simple intracell VCSEL monitoring. Each pixel has three individually addressable oxide-confined and substrate- removed 850-nm-wavelength VCSELs directly flip bonded to the mesas that are extremely close-spaced to permit equal butt coupling to 50-mum-core-diameter multimode fibers (MMFs) without the need for external coupling optics. Built-in radial VCSEL-to- fiber launch offsets as small as 7.8 mum were reached, leading to offset coupling penalties of only 0.4 dB. Quasi-error-free transmission of 10 Gbit/s signals is achieved over 500-m-long MMFs even under offset launch conditions. New opportunities for a range of further applications offered by high-density VCSEL arrays are discussed.