Polarization degenerate micropillars fabricated by designing elliptical   oxide apertures
  A method for fabrication of polarization degenerate oxide apertured micropillar cavities is demon- strated. Micropillars are etched such that the size and shape of the oxide front is controlled. The polarization splitting in the circular micropillar cavities due to the native and strain induced bire- fringence can be compensated by elongating the oxide front in the [110] direction, thereby reducing stress in this direction. By using this technique we fabricate a polarization degenerate cavity with a quality factor of 1.7*?10^4 and a mode volume of 2.7 u?m3, enabling a calculated maximum Purcell factor of 11. 
Morten P. Bakker, Ajit V. Barve, Alan Zhan, Larry A. Coldren, Martin   P. van Exter, and Dirk Bouwmeester
physics.optics cond-mat.mes-hall quant-ph