Photoluminescence polarization in individual CdSe nanowires

The polarization of the photoluminescence (PL) spectra of individual CdSe nanowires grown parallel and perpendicular to the c axes of the wurtzite structure was studied. Both the excitation and emission of the nanowires show strong polarization dependence. Maximum PL intensity is obtained when the excitation field polarizes parallel to the long axes of the nanowires, regardless of their growth directions. The emission polarization of the nanowires also does not depend on the growth direction, but is mainly determined by the elongated shape of the nanowires. The origin of the polarization is considered mainly a result of the large contrast in dielectric constants between the CdSe nanowires and their surroundings, while the contribution from the symmetry of the crystal structure is negligible.