We have studied the polarization characteristics of stripe geometry GaAs-Ga1-x AlxAs DH lasers with masked and selective thermal oxidation structure and found that the laser beams consist of both TE and TM modes with nearly the same intensities and are out of phase. The phenomena are quite different from the conventional semiconductor lasers in which the TE mode will be expected. A qualitative explanation for the above anomalous polarization charac-teristics is presented in view of the stresses and photoelastic effects in the active region.