VECTOR VORTICES AND POLARIZATION STATE OF LOW-ORDER TRANSVERSE-MODES IN A VCSEL

Transverse pattern selection and spatio-temporal dynamics in the compe tition among and superposition of first order Gauss-Hermite modes in a quantum well VCSEL are sensitive to birefringence and astigmatism. Wh en modes of different spatial pattern and/or polarization state are fr equency degenerate, the only stable solutions are those with doughnut intensity patterns. Patterns with orthogonal polarizations for the two constituent spatial modes are far more stable than plane polarized do ughnuts. For weak anisotropies (birefringence and/or dichroism) the pa ttern is stationary with a locally time independent intensity (though the polarization state differs from position to position). When the an isotropies are strong, the emission becomes time dependent with two sp ectral components in the optical spectrum, each with a different patte rn and polarization. (C) 1997 Elsevier Science B.V.