We show quantitatively how the limited polarization stability of vertical-c
avity semiconductor lasers is related to the small dichroism and large quan
tum noise in these lasers. We introduce several techniques to measure this
dichroism and noise. Suitable polarization projections are shown to yield e
ither the heterodyne beat or the partition noise of the two polarization mo
des. (C) 1999 American Institute of Physics. [S0003-6951(99)03816-4].