Polarization splitting of the gain band in quantum wire and quantum dot arrays

We theoretically predict and experimentally confirm that arrays of resonantly amplifying quantum wires and quantum dots (QD's) exhibit splitting of the gain band into separate bands for E- and H-polarized field. This effect originates from the diffraction at single anisotropically shaped QD's and the collective effect of the anisotropy of the QD array both described by an effective medium approach. Experimental results for multiple sheets of ZnₓCd_1-xSe QD's in a ZnSe matrix confirm the theoretical predictions and signal the discovery of a new class of ``active'' composites.