Optical polarization in vertically coupled InGaAs quantum dots of p-type modulation doping

We have investigated the polarization effect of optical process in the vertically coupled InGaAs quantum dot (QD) triple layers by varying the thickness of GaAs spacer layer. The transverse electric (TE)/transverse magnetic (TM) ratio for the ground state emission decreases from near 4 to 1.5 as the spacer thickness decreases from 40 to 5 nm. The TE polarization (in-plane polarization) is anisotropic with a stronger component along View the MathML source direction; p-type modulation doping further decreases the TE/TM ratio to r=1.2 for the strong vertical coupling QD structure of 5 nm spacer.