Spatially resolved Stokes parameters of small area oxide-confined Vertical-Cavity Surface-Emitting Lasers

Because of their cylindrical geometry and the consequent astigmatism free circular beam shape, Vertical-Cavity Surface-Emitting Lasers (VCSELs) are on the one hand appropriate structures for optical data communication. On the other hand, their fragility for undesired polarization instabilities due to their circular symmetry limits their usefulness for polarization selective applications. To understand the complex polarization behavior, one has to fully characterize the state of polarization e.g. in terms of Stokes parameters. With these four parameters S0, S1, S2 and S3 the state of polarized and unpolarized light can be described completely. We will present spatially resolved Stokes parameters for three different pump currents of a representative VCSEL with a small aperture sizes of 2μm.