Coupled VCSEL arrays: Active photonic lattices

Summary form only given. The coupled-lasing modes of the VCSEL array represent the allowed bands of propagating Bloch waves in the two-dimensional active photonic lattice. Previous positive-index guided VCSEL array designs have attempted to select a single-mode (i.e. all elements phase-locked) from the allowed bands of guided modes of the 2-D photonic lattice. All previously reported phase-locked 2D VCSEL arrays operate in either out-of-phase mode or a mixture of various modes, characteristic of weakly-index guided arrays, with poor intermodal discrimination. To achieve in-phase-like emission characteristics, external phase-shifters have also been used on optically pumped VCSEL arrays however the resulting beam is quite broad. The progress in phase-locked 2-D VCSEL arrays parallels closely that of edge-emitting phase-locked arrays. Weak coupling and poor intermodal discrimination found in evanescently coupled edge-emitting laser arrays has severely limited their single-mode output power due to gain spatial hole burning at the array level.