Estimation of in-plane superluminescence in vertical-cavity surface-emitting lasers

`In-plane´ superluminescence (IPSL) in VCSELs is analysed in the framework of the ray approximation. The results show that, for typical geometry and dimensions of vertical-cavity surface-emitting lasers, the IPSL can play an important role and lead to significant additional losses (referred to vertical lasing) of pump power for large diameter devices (10-100 μm). It is found that, for AlAs/GaAs device diameters in excess of about 50 μm, the IPLS can become sufficiently large such that lasing along the radius may result