Spatially resolved Stokes parameters of small-area vertical-cavity surface-emitting lasers: experiment and simulation

We present experimental investigations on spatially resolved Stokes parameters of vertical-cavity surface-emitting lasers (VCSELs) with a small aperture diameter of 3 μm and a monolithically integrated surface grating on top of the structure to technologically control the polarization. As expected, the grating fixes the state of polarization, but still shows both a spatially nonuniform linear polarization distribution of the fundamental transverse mode as well as an interesting eight-lobe pattern of circular polarization in terms of change of sign. These experimental findings are reproduced by numerical simulations using a fully vectorial three-dimensional model.