Dual-purpose VCSELs for short-haul bidirectional communication links

The operation of a new dual-purpose vertical-cavity surface-emitting laser (VCSEL), which functions either as a laser or as an avalanche detector, is presented. The original laser structure is modified by focused ion beam etching, enabling photodetection operation, with avalanche gain in excess of 10 available under reverse bias. Successful operation of a 2-Gb/s link employing two dual-purpose VCSELs as "ping-pong" transceivers is described. The noise performance is also examined.