We have studied the interaction between two optically pumped vertical-
cavity surface-emitting lasers (VCSELs) on a wafer as a function of th
eir separation d. The VCSELs are strongly coupled for d less than or e
qual to 13 mu m, leading to the appearance of higher-order lateral mod
es. For d greater than or equal to 13 mu m the VCSELs are weakly coupl
ed, leading to phase locking of the individual emitters. (C) 1996 Amer
ican Institute of Physics.