Higher-order transverse modes in possible nitride VCSELs

Excitation of various radiation modes during a possible room-temperature continuous-wave operation of nitride vertical-cavity surface-emitting lasers (VCSELs) is investigated and compared using the effective frequency optical model. Nitride VCSELs of a traditional design with two ring contacts have been found to exhibit unavoidable multimode operation which follows from an extremely non-uniform current injection into their active regions. To enhance desired single-fundamental-mode operation, current injection into active regions should be at least uniform, which may be realized using e.g. a special design of nitride VCSELs with an additional semi-transparent contact, two tunnel junctions and a double multiple-quantum-well active region.